Crank Length Calculator

Crank Length Calculator

Use our crank length calculator to find your perfect crank length. Bikes are usually sold with only 1 length of crank, whereas bike riders’ legs come in a large variety of sizes. Therefore it makes sense to use cranks that are relative to the rider’s leg length. (The calculator works for most types of bikes except recumbents).

How to Use the Crank Length Calculator

1) Measure your inseam (barefoot from the ground to the top of your crotch)

how to measure inseam for the Crank Length Calculator
How to Measure Inseam for the crank length calculator

2) For any distance bike riding like road, gravel, touring, XC MTB, etc – the calculator should give you an exact length. If you’re an MTB trail or enduro rider you can deduct 5mm.

For downhill and BMX you can deduct up to 10mm. (Remember you should not exceed the length given, but you can go shorter if you wish).

Note: The crank length calculator only provides an estimate of your ideal crank length in relation to your leg length. If you are unsure, check with a professional bike fitter.

Questions and Answers

Do Longer Cranks Improve Pedalling Efficiency?

No. It’s important not to use cranks that are too long, as it can cause discomfort, and force you to run your saddle too low. There’s a common myth that longer cranks increase power and pedalling efficiency, however, this has been proven not to be the case (see a study here).

For many mountain bikers and BMX riders, it’s often worth using shorter cranks as it helps prevent pedal strikes, also allows manufacturers to lower the frames BB – which can improve cornering, and also helps put the rider in a better position on the bike.

Are My Cranks Too Long?

If your cranks are longer than what our calculator recommends, then you might want to consider getting shorter cranks. If you are unsure, check with a specialist bike fitter for recommendations.

Are Shorter Mountain Bike Cranks Better?

Shorter cranks for mountain bikes are most likely an improvement. Paul William released a study that showed mountain bike riders reached their maximum power faster with shorter cranks. Also, shorter cranks are less likely to catch obstacles while pedaling off-road.

Does Crank Length Affect Saddle Height?

Yes, crank length affects saddle height. The longer the cranks the lower the saddle, the shorter the cranks the higher the saddle.

Are 175mm Cranks Too Long?

It depends on your leg length. Try our crank length calculator to give you a base value. 175mm cranks could be too long, too short, or just right!

Do Longer Cranks Increase Power?

No. There have been many studies that clearly indicate that crank length does not have an impact on power. You can see a study here by Jim Martin.

Final Thoughts

The most recent studies indicate that longer cranks are not always better (despite common belief). When choosing crank length, you need to consider the length of your legs and the type of riding you intend on doing.

However, you need to realize that the correct crank length is all about comfort and function, but not performance. It may surprise you to know that the power difference in crank length from 145mm to 170mm is only 1.6%. So give or take 5mm will have next to no effect on power.

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Peter Ballin

Pedro is the primary writer on the site. He’s raced downhill and enduro at a high level, spannered at mountain bike world cups, and also written a book called Mountain Bike Maintenance. He’s appeared in both print & online major media publications across the Uk, France, and Japan (and even appeared on French Television). He’s made his living from bikes in various forms, from mountain bike guiding in France and Spain, Trail building in New Zealand and Canada, and working as a bike mechanic in the French Alps for many years. Pedro loves a good adventure and is often settling random challenges like riding down Mount Fuji, swimming across Lake Geneva, and hitchhiking across America.