How To Measure A Bike Frame: A Complete Guide

Riding a bike with the wrong sized frame can cause problems, such as back pain and knee pain, but it can also make you ride without the proper form.

A bike that fits you properly is more comfortable and makes the experience much safer and more enjoyable.

Therefore, it’s crucial to know how to measure bike frame size before buying a new bike. This way, you’ll have a bike that suits your height and body shape so you can get the best out of it.

In this article, we’ll be covering:

  • The Importance Of Knowing How To Measure A Bike Frame
  • Understanding Seat Tube Length
  • How To Choose The Correct Bike Size Bike Frame For Your Height
  • Is Bike Fit Any Different For Women’s Bike Frames?

Ready to learn how to measure a bike frame?

Let’s get started!

How To Measure A Bike Frame: Title Image

The Importance Of Knowing How To Measure A Bike Frame

Riding a bike with the incorrect frame size will make your rides less enjoyable. But more importantly, you stand a good chance of hurting yourself.

Over time, your poorly fitting bike may cause aches, pains, and injuries. You can tweak your bike’s geometry by altering your handlebars, seat height, and crank length to make it more comfortable to ride. But knowing how to measure a bike frame will give you a good starting point.

4 Common Issues With Riding The Wrong Sized Bike

#1. Knee pain

If your knees hurt from riding your bike, your frame may be too big for you. Alternatively, your seat may be too high, or your cleats on your clipless pedals could be set up incorrectly.

Therefore, a slightly smaller frame could solve your problems. However, you should start adjusting your seat height or using cleats with more float.

#2. Back pain

If you experience back pain from cycling, your frame may be too small or too large. For example, if your bike frame is too large, your “reach” may be too much of a stretch for you.

However, if your reach is too small, you will be hunched over too much, causing stress in your back.

But your back pain may not be caused by your bike at all. Your problems may stem from a weak core, which could be remedied by some strength training, incorporating abdominal exercises.

#3. Shoulder/Arm/Neck Pain

Upper body pain can be caused by how you position yourself on the bike. If you’re sat too far forward or backward, you get stress in the upper body by not holding onto the handlebars properly.

Your bike could be too short or too long for you, but you may be able to fix this problem by changing your handlebars for ones with a different rise or a different stem.

#4. Hip pain

Like knee pain, you may experience hip pain if your bike frame is too large or your saddle position is incorrect. Try a different saddle height or slide it forwards or backward to support you correctly.

A woman cycles up a steep road at sunset.

Seat Tube Length

The length of a bike’s seat tube makes a difference in how well you can comfortably ride the bike. This measurement determines the maximum and minimum height you can set your saddle. It also dictates how low you can drop the saddle, which is vital for mountain bikers tackling steep descents.

However, you need to compare the seat tube length with the bike’s reach, as this makes a difference to how the bike handles and fits you. When you do this, you’ll know how long the bike is relative to your height.

You should pay attention to the “reach to seat tube ratio,” as two different bikes may be labeled a medium, but the seat tube lengths will fit different riders.

Two Ways To Determine The Seat Tube Length

#1 Check The Bike’s Size As Stated By The Manufacturer

The seat tube is the upright tube that holds the bike’s seat post. You should find a label towards the bottom of the tube, indicating the bike’s frame size.

Not all bikes have this label, but it is worth looking for, as it will save you from hunting down your tape measure. If there is no size label, you will need to measure your seat tube.

#2 Measure Your Seat Tube

Run your tape measure from the center of the crank to the top of the seat tube. Make sure you set your tape measure to the center of the crank to the very top of the tube for the true size. You may want to remove the seat post to help you be more accurate. 

This measurement is the frame size and will almost always be somewhere between 21 and 23 inches (53–58 cm).

Road bikes are sized in centimeters, so if you are in the U.S and measured in inches, you’ll need to convert your measurement.

To convert inches to centimeters, multiply your measurement by 2.54 to get the size in centimeters. Or you could use this converter to make it even easier!

If you are dealing with any other kind of bike, stick with inches, as this is what most manufacturers use. 

A man drifts around a dirt track corner at high speed.

How To Choose The Correct Bike Frame Size

Now that you know how to measure a bike frame, you need to know how to get the right size. This is where you need to measure yourself so you can start to look for bikes that fit you.

Measure Your Inseam

To measure your inseam, stand barefoot with your feet shoulder-width apart. Place a hardback book between your legs at your crotch.

Have someone measure the distance from the ground to the top of the book in centimeters. It is essential to ensure your measurement is from your actual crotch and not the distance between the floor and the crotch of your pants.

If you’re measuring for a road bike, multiply the measurement by 0.7. The reason for this is to shorten the inseam measurement, so you don’t end up with a bike with a seat tube precisely the same length as your inseam.

If you’re buying a new mountain bike, multiply your inseam measurement by 0.66. Mountain bikers use this smaller number as their bikes have chunkier tires than road bikes, elevating them off the ground more.

Choose A Bike To Fit You

You can now use these measurements to find a bike frame that fits you. The seat tube height and the inseam will correspond to the manufacturer’s bike size chart, usually found on the bike manufacturer’s website.

While looking at the size chart, check out the reach. This figure determines where you’re positioned on the bike and how big it feels.

If you want a racy feel to your road bike, you may want to choose a bike with a longer reach. On the other hand, if you’re a beginner, you might want to opt for a shorter reach, giving you a more upright riding position.

Your reach should balance comfort, control, and pedal efficiency.

Take A Test Ride

Before you buy a bike, it’s best to sit on one and take it for a test ride. At the bare minimum, you should ride the bike around a parking lot to see how it feels, handles, and stops.

When riding the bike, your shoulders should feel relaxed, with your elbows slightly bent. Your knees should also have a slight bend at the bottom of the pedal stroke.

In addition to this, you should feel no pain in your upper body while holding on to the handlebar grips. Neither should your hands get tired too quickly.

You may be able to improve the feel of the bike by moving the shifters and brake levers to a more optimum position.

A woman looks down at her bike in a forest.

Is Bike Fit Any Different For Women’s Bike Frames?

Men and women are physiologically different, so some bike manufacturers build bikes specifically for women.

In reality, anyone can ride any bike as long as it fits them correctly. Proper fit means comfort, optimum performance, and more fun. Some women find that riding a bike specifically designed for women is better for them, while others are perfectly happy with either unisex or mens’ frames.

There are two approaches manufacturers use when it comes to women’s bikes.

The first way is to use a unisex frame with generic geometry figures that suit men and women. They’ll then fit them with components specifically designed to suit women, such as women’s saddles and handlebars.

The second approach uses data from female cyclists to build specific frames to suit them. Manufacturers use the data to optimize the frame to suit female riders.

However, many bike manufacturers have gone away from women’s bikes and only build unisex bikes in recent years.

A man and a woman talk over their bikes on a road by the coast.

Now You Know How To Measure A Bike Frame

Knowing how to measure a bike frame is a great starting point to getting a bike that will suit your body shape. But, you’ll benefit from booking an appointment with a professional bike fitter.

A bike fitter will use formulas based on your measurements to select the best bike for you. They will also ensure that your handlebars and cranks are right for you while setting the optimum seat post height.

found this article helpful? check out these Guides from the BikeTips Experts below for more cycling Advice!

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One of BikeTips' regular content creators, Tom lives in the French Alps. When he isn't writing, he can be found charging downhill on a mountain bike or snowboard. Tom's other passion is fitness, which goes a long way to help him make the most of the Alpine lifestyle.

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