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A DIY bike fit with your phone

July 22, 2026 · 6 min read

A professional bike fit measures a handful of joint angles while you pedal and adjusts the bike until they land in proven ranges. The measuring part no longer needs a studio: a 20-second video on a trainer and a pose model will give you the same five angles fitters start from.

Where the five bike-fit angles are measured A rider from a real trainer clip. The bottom bracket is the centre of the circle the ankle traces while pedalling. Saddle and bar follow from the hip and the wrist. 1 2 3 4 5 Measured at 1 Knee flexion 2 Hip closure 3 Torso angle 4 Elbow bend 5 Ankle Derived from the clip saddle, bracket, bar the path the ankle traces At the bottom of the stroke this rider’s knee reads 36° Bottom bracket derived from the circle the ankle traces over 108 frames of pedalling.
A real rider, at the bottom of the pedal stroke. The bike underneath is derived rather than drawn: an ankle traces a circle while pedalling, so a least-squares circle through the ankle across 108 frames puts the bottom bracket at its centre, and the saddle and bar follow from the hip and the wrist. Only the drive-side limbs are shown.

The five angles that matter

Knee extension at the bottom of the stroke

The saddle-height angle. At the 6 o'clock pedal position your knee should keep 34 to 48° of flexion from straight. Less than that (leg too straight) usually means the saddle is too high. This can cause posterior knee pain and rocking hips. More flexion than that means it's too low, loading the front of the knee.

Hip angle at the top of the stroke

This is the closed angle between your torso and thigh when the pedal is at 12 o'clock, when your hip is tightest during each revolution. Fitters look for roughly 44 to 58° on a road position. Too closed and you'll feel it as hip impingement or a rocking pelvis. It's driven by saddle height, saddle setback, and how low your bars are.

Torso (back) angle

Measured from horizontal: 40 to 50° is a relaxed endurance position, 30 to 40° race-oriented, and TT/triathlon positions drop to 5 to 30°. Lower is more aero but demands more hamstring and back mobility. Chasing a pro's back angle without a pro's flexibility is the classic self-fit mistake.

Elbow angle

On the hoods, elbows should be softly bent, about 15 to 30° of bend, never locked. Locked elbows usually mean the reach is too long, and the road buzz goes straight to your shoulders. On TT extensions the elbow sits near 90 to 110° instead.

Ankle angle

The shank-to-foot angle stays near 90° (±15°) through the stroke. Excessive toe-pointing can be a sign the saddle is too high because the ankle extends to reach the bottom of the stroke.

Cycling target bands by preset The joint-angle target ranges the three built-in cycling presets apply, read from the application's own preset definitions. Target bands, by built-in preset road / race road / recreational TT / aero 0° 20° 40° 60° 80° 100° 120° Knee flexion at the bottom of the stroke Hip closure at the top of the stroke Torso angle from vertical Elbow bend (0° = locked straight) Ankle through the stroke
The target bands the three built-in cycling presets actually apply, read from the app’s own preset definitions. Race and recreational road fits differ most at the hip and torso. A more upright rider is a different rider, not a worse one. Torso is measured from vertical here, so a 45 to 55° band is the same position as “35 to 45° from horizontal”.

Measure yours in five minutes

  1. Put your bike on a trainer, camera at hip height, square-on to your drive side, far enough back to see the whole bike.
  2. Warm up for a few minutes first. Your position after 5 minutes of riding is your real position, so film ~20 seconds of steady pedaling then.
  3. Drop the clip into the analyzer, press Get Poses, and apply the Cycling: road fit preset (or TT / aero).
  4. Read the chart against the target bands: the knee curve's minimum each stroke is your bottom-of-stroke extension. The hip curve's minimum is your top-of-stroke closure. Torso, elbow, and ankle should ride inside their bands throughout.

Adjust like a fitter: one change at a time

Saddle height moves the knee angle roughly 1° per 3 mm. Make one small change, refilm, and use Compare to see both clips on one timeline. The before/after difference shows up in the curves immediately. Chase comfort first, aero second.

A DIY check like this catches big, common problems such as a saddle that is far too high or a reach that is far too long. Persistent pain, numbness, or saddle sores after your position is in range are the cue to see a professional fitter, who brings things video can't: cleat wedging, saddle pressure mapping, and a trained eye.

Try it on your own footage. Vi.S.In analyzes photos, video, and live webcam for free, right in your browser. No sign-up needed.

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