The number-one must-have when buying a new bike is finding one that fits your size. Whether you’re new to cycling or looking for an upgrade, choosing the right frame for you means you can ride in comfort and clock miles with ease. That’s where chatting with experts about fit and following bike size charts comes into play.

These days, almost everything can be bought online—and bikes are no exception. But the convenience of having your new bike delivered directly to your home comes with one main drawback: Unless you’ve already had a chance to try it out beforehand, you’re taking a gamble on getting the right size bike.

While buying a bike in person is much easier, it still helps to know what to look for in a bike size. Follow these steps and review our bike size charts below, and you’ll be ready to hit the road (or the trails) on the right bike in no time.

Consider the Bike Type

First, consider the type of bike you want to ride. Sizing varies greatly between road and mountain bikes, as well as between men’s and women’s models, and even between individual manufacturers. You’ll want to be familiar with your own wants and needs before determining what size is right for you. Many manufacturers also have their own bike size charts that will steer you in the right direction.

Know Your Height

While using your height as a guide is one of the easier ways to get an idea of your frame size, it won’t give you a perfect fit. Rather, it’s just a decent way to determine whether the frame will be too short or too tall. Below are general bike size charts for road bikes and mountain bikes, based on height. Keep in mind that this is only a general guide. Sizing will still vary between brands.

Road Bike Size Chart

Height → Bike Size (numeric) → Bike Size (T-Shirt)

4’10”-5’2” → 47-48cm → XX-Small
5’2”-5’6” → 49-50cm → X-Small
5’3”-5’6” → 51-53cm → Small
5’6”-5’9” → 54-55cm → Medium
5’9”-6’0” → 56-58cm → Large
6’0”-6’3” → 58-60cm → X-Large
6’3”-6’6” → 61-63cm → XX-Large

Mountain Bike Size Chart

Height → Bike Size (numeric) → Bike Size (T-Shirt)

4’10”-5’2” → 13”-14” → X-Small
5’2”-5’6” → 15”-16” → Small
5’6”-5’10” → 17”-18” → Medium
5’10”-6’1” → 19”-20” → Large
6’1”-6’4” → 21”-22” → X-Large
6’4”-6’6” → 22”-24” → XX-Large

Invest in a Bike Fit

Getting a professional bike fit before you buy can make all the difference. That’s why Missy Erickson, coach, fit specialist, and east coast director at Big Picture Cycling, recommends a getting a bike fit before you buy—and that goes for all athletes.“It doesn’t matter if you’re buying a new bike from a bike shop, ordering a bike online, or buying off Craigslist,” she says. “Knowing your fit dimensions and having a fit specialist help walk you through the process not only ensures you are getting the proper size, but a bike also for your specific needs.”

A bike fit will also provide all your more detailed measurements. For beginner cyclists and seasoned athletes, this can be extremely helpful. “Investing in a bike fit not only ensures you are going to get the right bike, but you’re also going to be set up on it perfectly, avoiding injury, pain, and discomfort, which will make cycling even more enjoyable than it already is,” Erickson says.

Try Before You Buy

It’s the most obvious and overused advice out there, but it’s true: Seeing a bike in person, trying it out, and getting a feel for it is often the best way to know if it’s right for you. Many bicycle brands and bike shops offer demo bikes in-shop or at demo events to allow customers to test ride them.

It also helps to ask questions and speak to knowledgeable staff members. As an added bonus, you avoid the potential damage from shipping, and you won’t have to assemble anything yourself.

Listen to Your Body

Ideally, you’ll know your approximate bike size before you buy. It’ll make the whole process easier, and you’ll be set up for success right from the beginning. But there’s always a chance you’ll follow a brand’s sizing information to the letter, and a bike’s fit feels off. This is okay. Bike fit isn’t an exact science. Rider height is an okay place to start, but it’s not a definitive metric. Things like your inseam length, arm length, and torso length all play a big part in what frame size is ultimately the right for you.

Sometimes, however, there are other ways to know if your setup isn’t right. Lower back pain, elbow pain, neck pain, and knee pain can all be indicative of a poor fit (among other issues). Numbness is another problematic sign. Keep an eye out for these markers, and if you’re experiencing them, consider that pro bike fit to help you figure out what’s wrong with your setup.

Inches and Millimeters? Pounds and Grams?

When it comes to bicycle sizes and dimensions, the industry uses a frightfully arbitrary combination of metric and imperial systems, sometimes shifting systems depending on the weight or dimension question. That’s if they’re not using some other—sometimes literally made up—system.

Mountain bike frame sizes are often listed in inches, while road sizes are usually listed in centimeters. But numeric frame sizing is falling out of favor as more brands adopt “T-Shirt” sizing (small, medium, etc.). And much like clothing, bicycle size designations are best used for comparing different sizes of the same bicycle and not for comparing one brand’s size to another’s. Because one brand’s “medium” might be another brand’s “small.”

Meanwhile, an increasing number of brands use their own sizing systems. For example, some Specialized mountain bikes use “S-sizing” (S1, S2, S3, etc.) which is based on choosing a frame size by how the bike feels on a ride rather traditional ideas about what is appropriate for a rider’s height.

Experienced cyclists—especially bike fitters and mechanics—are used to this madness and fluent in the dialect of bicycle weights and measures. But if you’re new to this world, it can be befuddling when the expert you’re talking with jumps from pounds to grams, inches to millimeters and so on while talking about a bike. Or if one brand’s sizing charts look nothing like another’s.

Yes, this is all extremely confusing. We know. Bicycling’s editors live in this world and still get tripped up. But proper bicycle fit is important for comfort, performance, and injury prevention and, unfortunately, most bicycles are not one size fits all like a car or motorcycle. So, take your time, triple check the numbers, ask lots of questions, and seek out second (or third) opinions.