The right saddle height: the formula is only the start

Saddle height is the adjustment with the biggest effect in the whole bike fit — and the first one to make, because anything set before it gets redone. The good news: it is not a guessing game. There is a computable starting point and a measurable decision criterion, and between them — 2–3 mm steps.

1. The starting point: 0.883 × inseam

Measure your inseam (floor to crotch, barefoot, with a book pressed horizontally) and multiply by 0.883. The result is the distance from the bottom bracket axle to the top of the saddle, measured along the seat tube. For an 85 cm inseam: 85 × 0.883 ≈ 75.1 cm.

The formula has two limits worth knowing: it ignores crank length (a 165 mm crank versus 172.5 mm means the saddle sits ~7.5 mm higher for the same leg extension), and it knows nothing about your flexibility, shoes, or pedals. That is why we call it a starting point — the calculator in our app adjusts it automatically for your declared crank length, and even then it is not a final decision.

2. The decision: knee angle, pedal at the bottom

The real criterion is biomechanical: with the pedal at the very bottom of the stroke, the knee should keep a slight bend — for most riders, an extension of roughly 140–150° (the exact range depends on bike type, position goal, and flexibility). Too much extension destabilizes the pelvis on the saddle and overloads the back of the knee; too little loads the kneecap and wastes power on every revolution.

That is exactly what the app's video analysis measures: you film 20–30 s of pedaling from the side, and the decision value is the median across revolutions, with a confidence indicator — not one lucky frame. If the angle sits in range, the saddle stays where it is, whatever the formula says.

3. How to adjust: 2–3 mm steps, one change at a time

Loosen the seat clamp, move the saddle 2–3 mm (mark the original position — a marker line on the seatpost is enough), tighten to the recommended torque, and ride a few minutes before re-measuring under the same filming conditions. Centimeter jumps feel efficient but skip past the correct position and confuse muscular adaptation.

4. What re-triggers the check

• A new saddle (padding thickness and shape change the effective height)
• New shoes or insoles (sole thickness enters the leg's chain directly)
• Any cleat adjustment — moving them toward the heel "shortens" the leg (see the cleat guide)
• Moving the saddle fore-aft — fore-aft and height influence each other: a saddle brought forward effectively drops, pushed back it rises (see the KOPS guide)
• A crank of a different length

5. Signs of a well-set saddle

A stable pelvis at normal cadence (no visible side-to-side rocking from behind), a heel that does not "chase" the pedal at the bottom, and a measured extension that sits in range revolution after revolution — a small spread between revolutions (the ± indicator in the analysis) is itself a good sign.

General, indicative guide. For persistent discomfort or special needs, a professional fitter remains our recommendation — they analyze from every angle, including asymmetries a side-view recording cannot see.