Bike type
trekking, city
5' 7"
bike frame size
Your inseam length should be in the 29.5-33.5" range
Inseam length
Bike frame size

With this bike size calculator, you can estimate the frame size of your new bike in the blink of an eye. Just choose the type of bike - road, mountain or general-purpose city/trekking bike, input your height and inseam, and we will recommend some bike frame sizes for you to take into consideration. If you're not sure how to measure inseam, or are still wondering "what size bike frame do I need?", just read on to find the answer. Also, we've prepared a bike frame size chart where you can find suggestions for mountain and road bike frame sizes.

How to measure inseam?

To find out your recommended bike frame size, you first need to measure your inseam - that is your inside leg measurement. Simply speaking, the inseam length is the distance from the floor to your crotch. So, how to measure inseam properly?

bike frame size
  1. Stand close to a wall, your feet should be 6-8" (15-20 cm) apart.
  2. Place a large, hardcover book between your legs - it will simulate the saddle.
  3. Mark where the book's spine touches the wall.
  4. Measure the distance from that point to the floor - that's your inseam.

Some formulas or charts use only the rider's height, but this leads to a less accurate estimation - you can have short, long or "average" length legs. As many different formulas exist, this bike size calculator won't show you only one number, but other frame sizes which may fit.

What size bike frame do I need?

bike frame size

With this bike size calculator we'd like to give you an idea which sizes of bike frames you should look at. But first we need to start with a general disclaimer - you should treat this tool as a guideline only. There are many different bike brands and models, so frames and general structure may vary a lot between them. Also, every cyclist is built slightly differently, and may have particular needs and preferences.

The frame size is usually measured as the distance between the top of the seat tube (where the seat clamp holds the seat post) and the center of the bottom bracket. Sometimes, the center or top of the top tube is chosen as the first point.

Our bike size calculator determines bike frame sizes on the basis of your inseam measurement. The formulas vary for different types of bike:

1. City/trekking bike frames

Trekking frame size = inseam [cm] x 0.64

2. Road bike frames

Road frame size = inseam [cm] x 0.67

This is the formula created in the '80s by Cyrille Guimard, famous French coach and former pro cyclist.

3. Mountain bike frames

Mountain bike frames are smaller than road bike frames. Usually, a frame shorter than 4 - 5 in (10 - 12 cm) is a good start

Mountain frame size = Road frame size - 11 [cm]

You probably noticed that the formulas don't take your height into account directly. However, when you choose your height from the drop-down list, a probable range of your inseam will appear (on average, it's around 47% of your height). This bike size calculator is suitable for both men and women, but not for children.

Bike frame size chart

You can find gazillions of bike frame size charts on the Internet. The problem is that they can vary a lot. Here we propose some conservative estimates of mountain bike frames and road bike frames.

Inseam [in] 25-25.5 26-27 27.5-28.5 29-30 30.5-31.5 32-32.5 33-34 34.5-35.5 36-37 37.5-38.5
Inseam [cm] 64-65 66-69 70-72 74-76 77-80 81-83 84-86.5 87-90 91-94 95-98
Mountain bike [in] 12-13 13-14 14-15 15-16 16-17 17-18 18-19 19-20 20-21 21-22
Road bike [cm] 43-44 44-47 47-49 49-51 51-54 54-56 56-59 59-61 61-63 63-66

We hope that after reading that short article and using our bike size calculator you will no longer wonder what size of bike frame you need. Just remember that all of these kinds of calculation should be taken with a pinch of salt - all in all, the best method is to try on different bikes. With professional bike fitting or even a simple trial and error process, you can find the perfect bike for you.

Different sizes for different purposes

You might have noticed that the recommended bike frame size will vary depending on the discipline you chose. This is partly because of how frames are designed, but is mostly due to the different requirements and priorities in each discipline. If your position on the bike changes, so will the bike frame size.

Let's start with mountain biking, which can be divided into several categories, but all of them have many similarities: a fairly upright position, wide handlebars and strong emphasis on comfort and bike handling. This means that a mountain bike frame will tend to be smaller than its road equivalent, allowing you to jump over obstacles and easily throw the bike around when riding "the gnarl".

On the opposite side of the spectrum we find road bikes. These too can be separated into many categories with "endurance" machines in the comfy end and "Time Trial (TT)" bikes on the performance end. In general, though, the smoother surfaces, higher speeds, and narrower handlebars favour for a more stretched positio,n with a larger distance between the saddle and handlebar.

However, keep in mind that these are only general remarks, with new developments and trends appearing constantly. Cutting-edge bikes might not follow these rules. Right now, road bikes are doubling down on the aerodynamic benefits of going low, narrow and stretched out. Mountain bikes (especially enduro and do-all machines) are getting longer, lower and slacker with every new model despite the humongously wide bars we tend to see fitted.

A bike ride a day keeps the doctor away 🚴

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Don't try to fit your bike, make your bike fit you

As a final note, it is important to remember that it is the bike that needs to fit you, and not the other way around. This is particularly important when one size of frame is designed to suit different people. So, once you get the right frame size, remember to check and tune everything to fit your body.

The first and most natural thing to do here is to adjust the seat post height so that your leg is extended at the bottom of the pedal stroke, while keeping a slight bend to your knee. This ensures optimal power output and prevents knee problems, with the only trade-off being that you probably cannot reach the ground with your feet while seated in the saddle.

The next step is to think about the position of your stem, the size of your stem, handlebars, cranks... and even saddle position within the seat post. The options here are almost limitless if we take into account that swapping parts is generally inexpensive and can totally transform your fit.

As always, the recommended way to go about fitting a bike to your body is to get a professional bike-fit. However, it may be very costly for most people, so the next best option is to go by feel and adjust things if you experience pain or discomfort after riding your bike. This is generally more than enough for everyone but the most committed amateur and professional cyclists, so try it yourself and find the perfect fit for you!

Hanna Pamuła, PhD candidate and Álvaro Díez

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Bike Size Calculator: Find Frame Size for Road, Mountain or City Bikes