How To Measure Inseam For Bikes: Explained By A Pro Bike Fitter

Pro bike fitter Robbie Ferri walks you through this essential measurement

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reviewed by Rory McAllister
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As a professional bike fitter, I know all too well that in the world of cycling, precision is paramount. From the curvature of handlebars to the choice of pedals, every detail affects performance.

Arguably the most important metric for bike fitters, however, is understanding how to measure inseam for bikes correctly. A proper inseam measurement ensures cyclists achieve optimal comfort, power transfer, and efficiency on their bikes.

In this comprehensive guide, I’ll share my professional experience working with real-world cyclists to delve into the intricacies of inseam measurement, exploring its significance in bike fitting and how it directly impacts a rider’s biomechanics and overall riding experience.

We’ll be covering:

Measuring tape on a blue background.

What Is Your Inseam?

The word “inseam” you will often hear in a tailors, but it’s also heavily used in cycling when it comes to your perfect bike fit.

The inseam is the length from where your legs separate between your legs at the hips down to the ground.

It can be very easily measured, and when looking to buy a bike, many manufacturers will go on inseam over height as it is a much more reliable measurement to help give you the correct bike size so it doesn’t end up getting returned.

Why Is The Bike Inseam Measurement So Important For Cyclists?

From beginners right up to professionals, knowing your inseam goes a long way when you’re a cyclist. Here’s why it’s important to know. 

1. Getting The Correct Frame Size

Whether you’re looking for a commuter bike or a gravel grinder, knowing your inseam can be a great bit of information when it comes to getting the right bike frame size. I personally think it’s the best way to roughly size a road bike.

There are many companies that use the inseam measurements in their size recommendations, and it can also allow you to check in advance that the bike has appropriate standover height above the top tube for you before you even get to your local bike shop.

2. Improved Bike Fit

Knowing your inseam will go a long way when having a professional bike fit. You can use the inseam measurement to calculate a good starting point for saddle height and a rough idea of crank length. It’s also good knowledge when looking at geometry for a fitter.

3. Accurate Clothing Measurements

Having knowledge of your inseam will also help when it comes to getting the correct clothing.

Checking the inseam length on the bib tights you may be looking at, or that pricey set of cycling shorts is very important. Once bibs have been tried on, retailers will not accept returns. 

4. It’s Useful In Understanding Your Bike’s Frame Geometry

Whether you ride a road bike or a mountain bike, one thing I have found very useful about knowing your inseam is that it can give you a clear indication of how aggressive a bike will be.

If you’re looking to buy a bike in a shop, quickly set the saddle height based on your inseam, and you can see how level it is with the handlebars. 

How To Measure Inseam For Bike Riders

Measuring inseam for bikes is very easy, and you can do it at home with simple things you will have lying around the house. Here’s what you’re going to need:

How To Measure Inseam For Bikes: Required Equipment

  • Your Cycling Kit
  • Book
  • Pencil
  • Measuring Tape
A book, pen, and tape measure. The tools to measure an inseam.
© Robbie Ferri/BikeTips

Step #1. Get In Your Cycling Kit

The first step is to get in the cycling kit you wear most often, or at least your bibs. Ensure you are barefooted, as that’s the proper way to measure the inseam.

It’s good to move around for a bit and maybe even jump on a bike to let the clothing settle in properly to the body. The size of the bib shorts pad makes a difference, which is why it’s a good idea to measure your inseam while wearing your kit. 

Step #2. Stand Against A Wall And Mark

Cyclist with a book in between legs about to measure inseam.
© Robbie Ferri/BikeTips

Next, you need to find a wall where you can make a pencil mark (alternatively, you could use a small blob of Blu-Tac, but that may not be as precise). You must then stand backward against the wall with your back flat on the surface.

Start pushing as much of your body against the wall as possible with your feet shoulder-width apart and flat on the floor. Then, you will want to take the book between your legs and push it as high as you can get it comfortably. 

Marking a book on the wall in the process of measuring in eam.
© Robbie Ferri/BikeTips

Then, hold the book against the wall, come away, and mark the top of the book. Having someone with you makes this easier, but it can be done alone.

Step #3. Measure

Measuring a inseam measurement.
© Robbie Ferri/BikeTips

Next, you will need to measure from the floor to the mark from the book and take note of the length using your tape measure. This will be your inseam measurement we will use in the next section to give you an example of how to set your saddle height. 

Converting Inseam To Saddle Height

Let’s use that inseam measurement to find a good saddle height. For example, say that the inseam you measured was 70 cm. The LeMond method is a great way to go. This is where you take your inseam and multiply it by 0.883.

70 x 0.883 = 61.81

So, a good place to set your saddle, for starters, would be just under 62 cm. This 62 cm will be the distance from the center of the bottom bracket, which houses the crank, to the center of the saddle.

Setting saddle height after measuring inseam.
© Robbie Ferri/BikeTips

This means you should have the correct leverage on your pedal stroke of roughly 25 to 40 degrees, depending on the bike fit. This should be close to your most efficient place for you to be pedaling. 

It’s important to mention that the LeMond method will give you a good starting point, but many other factors affect it, such as crank length, mobility, reach, and stack. It’s best to go and see a professional bike fitter, and they can get you perfect. 

You can also check out our Complete Guide to Setting The Right Saddle Height here!

Final Thoughts: How To Measure Inseam For Bike Riders

As a bike fitter and someone who rides in ultra-endurance races, I know the importance of having an excellent fit. A big part of that comes down to getting the saddle position and height correct, and the inseam measurement is key to finding that out. 

We highly recommend to any cyclist to start measuring inseam for bike and use the LeMond method to see if it’s near where it needs to be. If you are experiencing knee pain, the saddle height is the first place to look.

Whether you’re an MTB rider or a road cyclist, knowing how to measure your inseam is essential in finding right bike size for a new bike or to perfect the riding position on your current bike.

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Robbie has traveled the globe as an endurance athlete and bikepacker, breaking world records and competing in international ultra-cycling events such as the BikingMan series and the Transcontinental Race. He's also worked as an ambassador for some of the industry's leading names, including Shimano and Ritchey. If Robbie's not on a bike, he's either fixing them or out walking with his dog!

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