Bike Fit Calculator

A good bike fit is the difference between riding for hours in comfort and giving up after twenty minutes with a sore back and numb hands. This bike fit calculator takes your height and inseam and estimates a complete starting setup: frame size, saddle height, saddle setback, saddle-to-bar reach, and bar drop. It will not replace a professional fit, but it gets every contact point into a sensible ballpark before you ever turn a pedal.

The Five Numbers

• Frame size — from inseam, the foundation everything else builds on.
• Saddle height — inseam × 0.883, measured from the bottom bracket to the saddle top.
• Saddle setback — how far the saddle nose sits behind the bottom bracket, for balanced pedaling.
• Reach — the horizontal distance from saddle to handlebar, scaled from your height.
• Bar drop — how far the bars sit below the saddle (road bikes only); higher means more comfort, lower means more aero.

Why Proportions, Not Just Height

Two riders of the same height can need very different setups. Long legs and a short torso call for more saddle height but less reach; the opposite build needs the reverse. That is why this calculator uses both height and inseam — together they sketch your proportions far better than either alone.

Starting Fit Reference

Dialing It In

Set saddle height first and let it settle over a couple of rides. Adjust setback so that, with the crank horizontal, a plumb line from the front of your forward knee falls roughly over the pedal axle. Tune reach with stem length, and start with bars higher (less drop) — you can always lower them as your flexibility improves.

When to See a Fitter

If you ride long distances, race, or have any persistent pain — knees, lower back, neck, hands, or saddle area — a professional fit pays for itself. A fitter watches you pedal, measures joint angles dynamically, and accounts for things a formula never can: old injuries, asymmetries, and your specific flexibility.

Disclaimer: These are ballpark starting positions derived from body measurements alone. They do not replace a dynamic, in-person bike fit. Adjust gradually, and consult a qualified fitter or healthcare professional if you experience pain.