What is Bike Crank Length?
Bike crank length refers to the distance from the center of the pedal axle to the center of the bottom bracket axle on a bicycle. This measurement is crucial because it affects your pedaling efficiency, comfort, and overall performance on the bike. The right crank length can make your ride smoother and more powerful, while the wrong length can lead to discomfort and reduced efficiency.
Using The Calculator – Guide

Choose Your Unit: Select whether you want to enter your measurements in centimeters (cm) or inches (in) by clicking the appropriate radio button.

Enter Your Inseam Length: This is the measurement from your crotch to the ground. Input the value in the provided field.

Enter Your Height: Measure your full body height and enter it into the calculator.

Click “Calculate”: After entering your measurements, press the “Calculate” button to see the suggested crank lengths using different methods.
Calculation Methods
The calculator uses several wellknown formulas to suggest crank lengths:
Machine Method:
$1.25 \times \text{Inseam} + 65$
Lennard Zinn Method (Upper End):
$2.16 \times \text{Inseam}$
Lennard Zinn Method (Lower End):
$2.10 \times \text{Inseam}$
Graeme Obree Method:
$0.95 \times \text{Height}$
Each method provides a slightly different crank length, giving you a range to choose from based on your personal preference and riding style.
Example Calculations
Let’s say your inseam length is 80 cm, and your height is 175 cm:
Machine Method:
$1.25 \times 80 + 65 = 165$ mm
Lennard Zinn Method (Upper End):
$2.16 \times 80 = 172.8$
Lennard Zinn Method (Lower End):
$2.10 \times 80 = 168$ mm
Graeme Obree Method:
$0.95 \times 175 = 166.25$ mm
Based on these calculations, your ideal crank length might range from 165 mm to 172.8 mm, depending on the method you prefer.
Final Thought
Selecting the right crank length is essential for optimizing your cycling performance and comfort. Use this calculator to make an informed decision and enjoy a smoother ride.