Gravel bikes—also known as adventure or all-road bikes—are built to handle terrain ranging from forest service roads to pavement, dirt, and even mellow singletrack. In essence, they are more capable than road bikes yet more efficient than mountain bikes, making them a nice transition from daily commutes to weekend adventures. Our top recommendation for 2026 is still the Cannondale Topstone 1 because of its high-quality components, versatility, and price-to-performance ratio. If you're looking for something burlier, check out our Trail Mountain Bikes buyer's guide to see the best hardtail and full-suspension mountain bikes for a variety of uses and budgets.

Frame: Aluminum
Gears: 2 x 11
Tires: 700c x 38mm
Brakes: Hydraulic disc
What we like: Quality components and impressive versatility at a good price.
What we don’t: A bit heavy for weight-conscious riders.
We’ll start by saying that we didn’t anticipate our top gravel bike pick being an aluminum-frame rig, but the Cannondale Topstone 1’s versatility, smart build, and competitive price tag won us over. In terms of design, the Topstone features the kind of premium aluminum frame that the brand is known for, a gravel-specific Shimano GRX drivetrain complete with hydraulic disc brakes, and appropriately wide wheels for soaking up bumps. Its balanced geometry also hits a nice sweet spot of responsiveness for climbs and road riding with a relaxed and confidence-inspiring feel on the descents. The cherry on top: the mid-range “1” manages to undercut much of the competition in price at a reasonable $2,150. From weekend gravel rides to daily commutes, the Cannondale Topstone is an excellent option.
The aluminum frame comes with compromises, however. At about 22.5 pounds, the Topstone certainly isn't the lightest gravel bike on the market and likely won't be the first choice of speed-focused riders, and we’d like to see higher-quality rubber that’s tubeless-ready. However, these are relatively small nitpicks about an otherwise impressive all-around gravel bike. It’s worth noting that Cannondale also offers the Topstone Carbon with a lighter frame and their minimalist Kingpin rear suspension that helps cushion harsh impacts.
See the Cannondale Topstone 1

Frame: Carbon
Gears: 1 x 11
Tires: 700c x 50mm
Brakes: Hydraulic disc
What we like: Lightweight carbon frame, Shimano CN-LG500 drivetrain, and internal storage.
What we don’t: The unknowns of ordering consumer-direct.
Ari is a Utah-based brand that was one of the pioneers of consumer-direct bikes, which seek to cut out the middleman in order to offer the public better prices on high-quality builds. In addition to the carbon frame, the Shafer has many of the bells and whistles we've come to love from Ari mountain bikes, including a Shimano drivetrain and a storage compartment within the downtube. But for their gravel bike, Ari has added five mounting points for all of your water bottle cages and bikepacking accessories. The 69-degree head angle keeps you in a central position to be ready for whatever's in front of you, whether that's a daunting ascent or a heart-pounding downhill. All things considered, you'd be hard-pressed to find a gravel bike build at this price point with the quality and design the Shafer offers.
Depending on your preferences, there may be a couple of things that you'd find less than favorable about the Shafer. For one, the 1 x 11 drivetrain isn't for everyone–a lot of gravel riders prefer a front derailleur in order to really fine-tune power output. The same goes for the tires. 50 millimeter wide tires are pretty burly, and that's a notable amount of extra weight for those who are counting ounces. Small gripes aside, the Ari Shafer is a top-tier model at a mid-tier price, and we can't imagine having a bad time on this bike.
See the Ari Shafer

Frame: Aluminum
Gears: 1 x 10
Tires: 700c x 45mm
Brakes: Mechanical disc
What we like: Solid feature set for those dabbling in the sport.
What we don’t: Fairly heavy and middling performance overall.
For riders just dipping their toes into the gravel world, Co-op Cycles’ ADV gravel bikes have a lot of appeal. For one, it’s a fairly simple buying process: Co-op Cycles is REI’s in-house bike brand, which brings nationwide access to shops, easy assembly and maintenance, and a reliable warranty. And their ADV collection includes solid performers like the mid-range 2.1, which comes in at a very competitive $1,499. For this price, you get the entry-level microSHIFT Sword component group, which is well-made but comes with slight compromises like a 10-speed cassette (compared with 11 for the upgraded versions). You also miss out on some nice upgrades like hydraulic disc brakes, although the Tektro mechanicals are decent performers and don’t require much in terms of maintenance.
As expected, the ADV 2.1 shouldn’t be on the short list for those looking for a speedy machine, but the design in general is well-balanced. The Kenda Piedmont tires are proven performers, the wheels are tubeless-ready, and the bike has a sturdy feel to it in general. That said, it’s not an agile design, and the weight is decently high (REI gives it a median weight of over 23 pounds). As such, those looking for a longer-term investment may want to spend up to the Cannondale Topstone above—which is also sold through REI Co-op—but casual riders looking to add some gravel time to their weekends will likely be very happy with the ADV 2.1.
See the Co-op Cycles ADV 2.1

Frame: Carbon
Gears: 2 x 11
Tires: 700c x 45mm
Brakes: Hydraulic disc
What we like: Lightweight carbon frame and front suspension do a great job of taking the edge off while descending.
What we don’t: High tech and brand name come with a high price tag.
California-based Specialized is one of the biggest names in cycling, so it should come as no surprise that they offer a champion in the gravel-focused Diverge line. The most noteworthy feature is its suspension, which delivers a relatively high 20 millimeters of travel. Unlike many other gravel bikes, the Specialized bike focuses its shock absorption at the front rather than the rear. For anything from surprise impacts with rocks to rough washboard roads, this feature will considerably dampen your ride and reduce arm fatigue. The Diverge 4 Pro also includes in-frame storage with its unique and very functional SWAT system.
The obvious downside to the Diverge 4 Pro is the price–with this budget, you could buy a cheaper bike for you and your friend, and have enough budget left to go on a pretty epic trip to use them. Also, not everyone wants or needs suspension on a gravel bike, and the extra technology, moving parts, and maintenance certainly tack on some added costs to the overall price tag. Still, if pressed to recommend the ultimate gravel bike if budget is no issue, we'd have to say the Specialized Diverge 4 Pro is the one.
See the Specialized Diverge 4 Pro

Frame: Carbon
Gears: 1 x 12
Tires: 700c x 40mm
Brakes: Hydraulic disc
What we like: Typical Santa Cruz craftsmanship and attention to detail.
What we don’t: Not the best value.
Santa Cruz is lauded within the mountain biking community for their quality frames and remarkable attention to detail, and that reputation holds true with the gravel-oriented Stigmata. In recent years, the Stigmata was redesigned with additional clearance for tires up to 45 millimeters wide (as well as 650b tires), updated geometry with a slightly longer head tube that translates to a more upright and comfortable riding position, and internal routing for dropper seat post compatibility. What does all this mean for you? In short, the versatile Stigmata is now just as at home on the cyclocross course as it is on far-off backroad adventures.
Where does the Stigmata fall short? Like all Santa Cruz bikes, the gravel rig is undeniably pricey at $4,149 for the Apex model, which includes the high-end 800 groupset. For quite a bit less, other models on our list feature similar components but include a notable upgrade in ride quality over bumpy terrain with their proprietary suspension designs. That said, buying from Santa Cruz involves paying a premium for the brand’s attention to detail (all models are admittedly fantastic-looking), strong warranty, and reliable long-term performance.
See the Santa Cruz Stigmata GRX

Frame: Aluminum
Gears: 2 x 10
Tires: 700c x 38mm
Brakes: Mechanical disc
What we like: Good overall performance for a palatable price.
What we don’t: Downgraded drivetrain.
Better known for their extensive lineup of mountain bikes, Norco did a nice job with the dirt-focused Search XR A2. For a reasonable price, you get a 2 x 10 Shimano drivetrain that works well across most terrain, along with a healthy selection of mounting locations for racks, bottles, and gear. Further, you get thru-axles for a stiffer ride in the rough stuff and tubeless-ready wheels (in our opinion, it’s a no-brainer to set up your gravel bike this way for less weight, fewer flats, and more grip). While it can’t match the racing pedigree of the models dedicated to that use, the Search XR is an impressively capable companion for everything from backroad exploring to daily commutes.
At this price point, however, there are some entry-level components in the build. It’s nice to see Shimano GRX derailleurs and crank, but the shifters are from the road-focused Tiagra line, so they’re not as user-friendly on gravel. In addition, you get less-powerful mechanical brakes, and the tires aren’t the best in slippery and dicey conditions, so many backcountry explorers will want to upgrade those right off the bat. Flaws aside, this is a great budget-friendly gravel bike that can be used for anything from bikepacking to commuting, and anything in between.
See the Norco Search XR A2

Frame: Chromoly
Gears: 1 x 12
Tires: 700c x 45mm
Brakes: Mechanical disc
What we like: Quality chromoly frame and versatile geometry.
What we don’t: Heavier and more expensive than aluminum models.
The only chromoly frame on our list, the Surly Straggler is a gravel bike with a do-it-all personality. If you're unfamiliar with the material, chromoly is a chrome-molybdenum steel blend that is more durable, stronger, and more resistant to fatigue than aluminum. Although quite a bit heavier than the carbon and aluminum models above, the Straggler’s smooth-riding frame and classic design are ideal for those who prioritize comfort and durability over speed and new tech. Other notable features include a 1 x 12 drivetrain for ultimate simplicity, multiple mounting spots for racks and gear, and fender mounts for rainy-day commutes. From all-out touring to weekend gravel rides, the Straggler makes for a solid one-bike quiver.
The Straggler is not without its flaws. Other models in our lineup have a wider gear range, feature better stopping power with hydraulic rather than mechanical disc brakes, and include thru-axles for a more efficient ride. The Straggler is also devoid of bells and whistles, such as in-frame storage or suspension. All of that said, there’s a reason behind the saying “steel is real.” In short, it’s hard to ignore the ride characteristics, burly feel, and long-term durability of a chromoly build. If you take care of the Straggler, you'll probably be giving it to your kids someday.
See the Surly Straggler
One choice you’ll have to make when choosing a gravel bike is whether you want hydraulic or mechanical disc brakes. In short, the main differences between the two relate to power and ease of use. Mechanical brakes, as their name implies, use a cable system to actuate the brakes and slow you down. Hydraulic disc brakes, on the other hand, use fluid rather than cables to initiate the brakes. This means that hydraulic brakes provide better stopping power with less effort, are easier to control and fine-tune, and can’t get clogged with trail debris and mud (mechanical brake cables can easily get dirty and rust over time). In the end, the choice often comes down to cost: hydraulic brakes come with a bump in price, while mechanical brakes can be found on most budget-friendly models.
We appreciate that the Evil Bikes Chamois Hagar was built with high-quality components, and we are fans of the downhill-oriented geometry, as long as we are going downhill. The issue is that most gravel rides have a fair amount of climbing, and the Chamois Hagar is noticeably less twitchy and responsive while ascending than most models we've tested.
There's no denying that the Moots Routt YPP Force AXS is an impressive piece of equipment. The titanium frame, coupled with 20 millimeters of rear micro-suspension, makes for a ride quality that will satisfy the most dedicated of gravel cyclists, but we can't get behind the $10,000 price point.
| Bike | Price | Frame Material | Gears | Tires | Brakes |
|---|---|---|---|---|---|
| Cannondale Topstone 1 | $2,699 | Aluminum | 2 x 11 | 700c x 38mm | Hydraulic disc |
| Ari Shafer Sport | $2,549 | Carbon | 1 x 11 | 700c x 50mm | Hydraulic disc |
| Co-op Cycles ADV 2.1 | $1,499 | Aluminum | 1 x 10 | 700c x 45mm | Mechanical disc |
| Specialized Diverge 4 Pro | $7,999 | Carbon | 2 x 11 | 700c x 45mm | Hydraulic disc |
| Santa Cruz Stigmata Apex | $4,149 | Carbon | 1 x 12 | 700c x 40mm | Hydraulic disc |
| Norco Search XR A2 | $1,649 | Aluminum | 2 x 10 | 700c x 38mm | Mechanical disc |
| Surly Straggler | $2,699 | Chromoly | 1 x 12 | 700c x 45mm | Mechanical disc |
This guide was originally created in 2021 with 11 of the top gravel bikes on the market. Since then, it has shifted and morphed with innovations in technology and changes in pricing. Editor Ross Patton took management of the guide over in 2026. Born in Utah and practically raised on two wheels, Ross has logged rides all over the West, from several laps on the White Rim Trail to the Mojave Desert and all over the Sierra Nevada and Rockies. With a formal education in Environmental Science and more than 20 years of experience behind the scenes with outdoor products, you can trust that he knows the difference between a product he'd recommend to his friends and one that's better left in the warehouse.
We considered a hefty list of factors while choosing the 7 bikes to include in our guide. Our goal is to create a guide that covers all types of riders, from those who are new to the sport and looking to get some sweet views and fresh air to multi-night bikepackers to hardcore racers. We consider frame material (which directly relates to weight), wheel size and width, drivetrains, mounting points, and whether or not there are any extras, such as in-frame storage or suspension. Elements such as body positioning and responsiveness are subjective, but our team of two tire enthusiasts is here to give you the best guidance possible so that you can make an informed purchasing decision.
As their name suggests, gravel bikes are designed to be ridden on surfaces like gravel trails, doubletrack, and forest service roads. While people have been taking their road bikes onto unpaved roads for decades, this emerging category has a number of thoughtful design features that make the experience much more enjoyable. In general, you should look for frame clearance to accommodate up to 700c x 45mm tires, multiple mounting locations (three or more) for water bottles and food, longer wheelbases that are more stable at high speeds, and disc brakes to handle long descents over varying road conditions. Put simply, gravel bikes can continue on when traditional road bikes are forced to turn around, and they can easily handle the daily commute to work, too.
From the list above, you’ll notice that carbon and aluminum are by far the most popular materials for gravel bike frames. You also might come across chromoly (a chromium molymdenum steel blend) or titanium, but these are far less common. Carbon is the lightest material of the bunch and often the choice among gram-counters and speed-focused riders. Additionally, because carbon bikes are made with molds instead of welds, companies are able to better “tune” their ride characteristics, making them more compliant for comfort or stiffer for better power transfer and efficiency. Salsa’s Warbird, for example, has been through many iterations over the years in search of that perfect balance.
All that said, carbon bikes are quite pricey, and you can often get a similarly equipped aluminum model for hundreds of dollars less. Although heavier than carbon, aluminum typically is more durable, and even heftier steel and titanium rigs will stand up to years of use and abuse. For the majority of casual cyclists, we recommend sticking with an aluminum gravel bike simply to get the best bang for your buck.
Most gravel bikes come with one of two popular drivetrain options: 1x (which features a single front chainring and fewer overall gears) or 2x (which has two front chainrings and more gear options). We love 1x drivetrains for their simplicity, ease of use, and generally lower weight. And because of the fewer gears (typically 11-12 vs. the 16-22 found on 2x systems), we think they’re a great match for fit riders and those whose frequent rolling terrain as opposed to steep climbs and descents. That said, we prefer 2x setups for more mountainous terrain. Although they generally weigh a bit more than 1x drivetrains, 2x systems (like the 2 x 11 included on the Cannondale Topstone 1) typically offer the rider both an easier gear for the uphill and a harder gear for the flat sections. Of course, it’s possible to modify a 1x system with a larger-range cassette, but we prefer the convenience of sticking with the original components.
700c
In general, 700c wheels and tires offer the best overall performance for mixed-terrain riding, and they continue to be the most common option for gravel bikes. 700c tires are narrower than 650b options, usually weigh less, and roll faster on tarmac and most gravel paths. Further, when the time comes to replace your tires (or you simply need a different tread pattern that better suits your local terrain), there are significantly more options available in the 700c size. In the end, unless you spend the vast majority of your time on exceptionally rough gravel, we think 700c tires and wheels are the best choice for all-around riding.
650b
Alternatively, if comfort is your main priority or you spend almost all of your time on gravel, then a 650b tire and wheel combo makes a lot of sense. Although they are heavier and roll more slowly than 700c wheels, the larger footprint and lower air pressure allow them to float over obstacles much more smoothly. The bigger contact patch with the ground also translates to increased traction, which can be especially helpful on soft or loose sections of road. As gravel riding expands into increasingly rugged terrain, 650b tires are becoming more and more common (including our top budget pick, Kona Rove AL 650). However, if you consistently frequent pavement and mellow trails, you’ll probably be better served by 700c wheels described above.
Tires are an often-overlooked component, but as the only thing connecting you to the ground, they are an important consideration for gravel riding. There is no one-size-fits-all tire, but we do have some recommendations regarding tread patterns, sizes, and widths. For those who spend the majority of their time on pavement but like to explore the occasional gravel road or path, we’d pick something in the 30- to 32-millimeter range with a slick or herringbone tread pattern. In short, they roll fast on tarmac, weigh very little, and provide an ample amount of comfort and traction. Tires in the 35- to 38-millimeter range are more versatile and a great choice for those who split their time evenly between pavement and gravel. Tires in this size come in a variety of tread patterns, which cover everything from smooth slicks to knobby options (resembling mini mountain bike tires). In this category, we really like Schwalbe’s fast-rolling and surprisingly grippy 700c x 38mm G-One.
Last but not least, if you frequent gravel more than pavement, we recommend opting for a tire that is 40 millimeters or wider. While these larger sizes will be heavier and roll slower on pavement than the skinnier options above, the added comfort and traction they provide off-road is well worth the tradeoff. We’re particularly fond of two tire manufacturers at the moment: WTB and Donnelly. Both brands offer a solid lineup of sizes and tread patterns that cover everything from smooth road tires to aggressive gravel options. And one final note: if you’re upgrading or replacing tires on an existing bike, it’s important to make sure you have enough room for these larger sizes. At a minimum, we like 3 to 4 millimeters of clearance to account for mud and debris between the tire and frame.
One of the most important parts of bike setup is properly adjusting tire pressure, which is measured in pounds per square inch (psi). Too much pressure will result in bouncing down the path or road and feeling every little bump along the way. Too little pressure, on the other hand, will make you feel as though you’re riding with the brakes on and can result in flat tires or bottoming out your rims on rocks. The ideal tire pressure lies between these two extremes, but unfortunately, there’s no universal number—there simply are too many factors to account for, including rider weight, tire width, surface type, and riding style.
All that said, we do have some general advice on how to find an appropriate psi. To start, inflate your tires to the maximum pressure labeled on the sidewall. Next, lay an object larger than a pencil in your driveway or on the sidewalk—a wooden dowel or mixing spoon handle works great—and ride over it at a comfortable speed (about 10mph). You’ll likely feel the object beneath you. Lower your tire pressure by 3 to 5 psi and repeat this process again until you barely feel the item. Make note of this pressure and take your bike for a real ride. During your outing, think about how your tires feel and consider any adjustments that you might want to make (this goes for every outing, not just your first). While experienced cyclists might balk at this method, it’s a great way for new riders to understand and learn to adjust pressure based on conditions, terrain, and other factors. And a final note: we recommend running anywhere from 3 to 8 psi less in your front tire than the back, as most of your weight is over the rear.
Suspension isn’t common on gravel bikes, but it’s nevertheless important to explain for those looking for a smoother and more comfortable ride. From the picks above, the Trek Checkpoint SL 6, Moot Routt, and Specialized Diverge Sport all feature some sort of suspension-like technology or dampers to help take the edge off big potholes and washboard roads. We particularly like Trek’s IsoSpeed on the Checkpoint SL 6, which decouples the top tube and seat tubes to create a less jarring ride. Alternatively, Specialized focuses their tech at the front of the Diverge Sport, which they equate to about 20 millimeters of suspension travel. And finally, Cannondale's Kingpin rear suspension offers up to 30 millimeters of travel via a thru-axle pivot connecting the seat stay and seat tube. Price goes up with the added tech (Cannondale's Topstone Lefty 3 runs $4,250), but if you spend a good amount of time at speed on exceptionally rough roads, it may be worthwhile to consider one of the models listed above.
It almost goes without saying that a lighter bike will feel sprightlier and more responsive than a heavier rig on the road or path. Not only does it make the uphills more bearable, but it also allows you to cover ground more quickly with less effort. And performance benefits aside, we always welcome lifting less weight onto our rack. However, weight often correlates directly with cost: the more you spend on a bike, the less it will weigh. For example, the $1,599 Co-op Cycles ADV 2.2 tips the scales at around 23.5 pounds, while Santa Cruz’s carbon Stigmata Force 2X ($5,849) weighs just over 18 pounds. We think the sweet spot is in the 20- to 23-pound range for most riders, which will usually set you back roughly $2,000. Race-focused cyclists likely will be willing to spend up for less weight.
One of the best and least expensive upgrades you can make to your bike is upgrading to tubeless tires. The biggest benefit is the ability to run lower tire pressures, meaning the tires are better able to absorb impacts without increasing the risk of a pinch flat. This also translates to a larger contact patch with the ground, making them ideal for off-road use. Plus, eliminating tubes in favor of sealant can drop a little rotational weight from your kit.
All that said, it can be a challenge converting your bike to tubeless. While installation has become significantly easier over the last few years due to improvements in the technology, you still get the occasional tire-and-rim combination that just doesn’t want to inflate. You’ll also have to replace the sealant a couple of times per year—it has a tendency to dry and become ineffective at sealing small holes. And finally, tubeless setups can be a bit of a mess should you ever need to put a tube in your tire. If you don’t feel comfortable with the initial installation, we recommend asking your local bike shop for help.
In general, we prefer cross-country shoes and pedals on our gravel rigs. Why? While gravel bikes share a lot in common with road models, pavement-oriented shoes typically have smooth and flat outsoles that make walking on gravel uncomfortable and cumbersome. Alternatively, XC pedals and shoes are still lightweight yet feature a much more walkable and more comfortable outsole. For pedals, we like Shimano's clipless 520 SPD in particular—we’ve put over 5,000 miles on ours and have been very impressed. In terms of shoes, we recommend an option like Giro’s Cylinder or Shimano's XC3—they’re light, affordable, stiff enough for efficient power transfer, and still very comfortable for time spent off the bike. For a complete list of options, see our article on the best mountain bike shoes.
Tire Clearance
While gravel bikes bear a strong resemblance to both cyclocross and road bikes, there are a number of key differences to point out. For starters, while most modern road bikes max out at about 30-millimeter tires and cyclocross bikes at around 40 millimeters, gravel bikes typically are able to accommodate up to 700c x 45-millimeter or 650c x 50-millimeter tires. The main advantage of these beefier tires is their ability to run lower air pressure, which results in a more forgiving ride and greater traction. What are the downsides? They’re quite a bit heavier than something in the 28c range (often found on road bikes), but significantly more comfortable and confidence-inspiring on rough roads.
Geometry
Another key difference between these types of bikes is their geometry, or the measurements of the frame. Cyclocross models tend to have high bottom brackets to clear race course obstacles and shorter wheelbases for easier maneuverability at slower speeds. Gravel rigs, on the other hand, tend to be lower and longer for increased stability during fast-paced descents. Compared to traditional road bikes, expect to find slacker head tube angles as well as longer wheelbases, which again translate to increased confidence and stability while exploring rough roads with bumpy descents.
Mounts
Compared to road and cyclocross bikes, gravel grinders feature significantly more mounting locations for extra water bottles, bags, and gear. In general, long gravel rides pass through far fewer service areas, meaning you’ll need to stock up on food, water, and other gear before heading out. Cyclocross bikes are typically stripped of additional braze-ons for fenders or racks, both of which you’ll likely find on a gravel bike.
Those who already own a hardtail might be wondering: “Can’t I just ride my mountain bike on gravel roads instead of purchasing something new?” And the answer is a resounding “yes.” In fact, we actually encourage riders to use what they already have whenever possible. After all, people have been riding all sorts of bikes on dirt roads for decades—long before the advent of this niche category.
All that said, there are many benefits to purchasing a true gravel-focused bike. These gravel-grinding machines are significantly lighter than mountain bikes, the drop bars offer multiple hand positions for all-day comfort, and you get more mounting locations for food, water, and gear. Gravel bikes also feature a wider gear range for the varied terrain you can expect on forest service and backroads. While a hardtail with skinny tires certainly will do the trick (we did this for quite some time), for those who plan on spending a lot of time on pavement and gravel, it’s hard to ignore the performance differences. There's good reason why this is one of the fastest-growing bike categories.
First and foremost, we fully encourage you to shop at your local bike shop whenever possible. There's just no replacement for a great local shop, the bike and trail advice that goes with it, and the ability to ride a certain model beforehand and easily get replacement parts and service. Having said that, buying online certainly has its benefits. It's incredibly easy to compare specs, prices, and parts online, and bike selection and shipping have improved dramatically in recent years.
There are a few key questions you should ask yourself before beginning your search. Do you know which size bike you need? Are you comfortable with some assembly? How much will shipping cost? Like shopping for the best bike helmets, it can be challenging—and especially for first-time buyers—to determine the right-sized bike from the comfort of your couch. To help, many major online retailers such as REI Co-op, Jenson USA, and Backcountry provide geometry charts and size recommendations for most of their models. Others, like Competitive Cyclist, also feature bike-fit tools that should help you determine your correct size.
If you choose to go the online route, most bikes shipped to your home will require some assembly. Some simply require throwing on the front wheel and pedals, but others will need an extensive amount of work before they’re ready to ride. This can include cutting the steerer tube, installing drivetrain parts, and carefully adjusting components for proper alignment. It’s also not uncommon to pay an “oversized” shipping fee. For example, Backcountry and REI often have an additional charge for shipping a bike, although REI offers a free ship-to-store option, which is a great alternative for buyers who want the added benefit of employee advice and expertise. In the end, it depends on how comfortable you are choosing, sizing, and assembling a bike.