How do I measure my inseam?

Stand barefoot against a wall with feet 15 cm apart. Place a hardback book between your legs, spine up, pressed against the wall. Measure from the floor to the top of the book spine.

Is frame size the only thing that matters?

No. Frame size is a starting point. Stack, reach, top tube length and seat tube angle all affect fit. A professional bike fit is recommended for optimal comfort and performance.

What if I am between sizes?

For racing, go smaller (more aggressive position). For comfort and touring, go larger. Many modern bikes come in S/M/L rather than centimetre sizes.

Does the formula differ by bike type?

Yes. Road bikes use inseam x 0.665, mountain bikes use x 0.59 (smaller frames for clearance), and gravel bikes use x 0.645.

BikeCalcs

Frame Size Calculator — Find Your Bike Size

Find the right frame size based on your body measurements and bike type.

Inseam Length

Length measurement

Height

Height measurement

Bike Type

Enter the bike type

How We Calculate This

Frame Size Calculation

Frame Size (cm) = Inseam (cm) x Bike Type Factor

Road bike: x 0.665
Mountain bike: x 0.59
Gravel bike: x 0.645
Touring bike: x 0.66

The standover height is calculated as inseam minus a clearance margin (2 cm for road, 8 cm for mountain bikes).

Frequently Asked Questions

Related Calculators

Saddle Height Calculator

Calculate optimal saddle height from inseam measurement.

Handlebar Reach Calculator

Determine ideal handlebar reach from torso and arm length.

Stack and Reach Calculator

Compare frame stack and reach between different bike sizes.

Stem Length Calculator

Calculate the stem length needed for your ideal reach.

Crank Length Calculator

Find optimal crank length based on leg length and riding style.

Last updated: 2025-02-20

All calculations are estimates. Always verify results and consult a professional bike fitter where appropriate.