Crank Length and Saddle Height: How to Adjust When You Change Cranks

Saddle height is measured from the centre of the bottom bracket to the top of the saddle. At the bottom of the stroke the pedal sits one crank length below that centre, so how far your leg extends at the bottom depends on both saddle height and crank length. With a shorter crank the pedal does not go as low, so your leg extends less at the same saddle height.

At the top of the stroke it works the other way: a shorter crank brings the pedal less high, so your knee and hip close a little less there.

The base formula (inseam × 0.883) assumes a 170 mm crank. If you enter your crank length, the calculator changes saddle height by the difference, millimetre for millimetre: adjustment = 170 − your crank length. The final height is rounded to the nearest millimetre.

Using FitInspector’s method, move the saddle by the difference between your old and new crank length: shorter cranks — raise the saddle; longer cranks — lower it. For example, going from 172.5 mm to 165 mm cranks means raising the saddle by about 7.5 mm.

Then check the result: measure your knee angle at the bottom of the stroke with the position check. See knee angle in bike fitting for the target ranges.

This section is separate from the calculator’s method. Two recent studies looked at small changes in crank length.

• Reynolds et al. (2025), Sports Biomechanics. 14 amateur cyclists rode at their preferred crank length (165–172.5 mm) and at ±5 and ±10 mm, with joint angles measured by 3D motion capture. Shorter cranks led to significantly less knee and hip flexion during parts of the pedal stroke, more forward pelvic tilt, and less sideways and rotational movement at the hip and knee. Mean power output did not change. The authors discuss a hypothesis that this could lower the risk of overuse injury; the study did not measure injuries, so that remains a hypothesis, not an established outcome.
• Li et al. (2025), Journal of Exercise Science & Fitness. 28 trained male amateur road cyclists rode 165, 170 and 175 mm cranks. There were no statistically significant differences in cycling economy or in 6-second sprint power and cadence. Perceived exertion was lower with 165 and 170 mm than with 175 mm; 165 and 170 mm did not differ.

FitInspector does not recommend a crank length: its methodology has no formula for it. One possible reason riders explore shorter cranks is feeling cramped at the top of the pedal stroke — for example, the hip feeling very closed in a low position. That is a reason to try, not a diagnosis, and shorter cranks are not guaranteed to help. If you try them, adjust the saddle as above, judge by comfort and how you ride over several sessions, and consider asking a bike fitter to help you test.