How to take bike fit photos that measure accurately

Put your bike on an indoor trainer on level ground, with space to stand back several metres to the side. Check the bike is level — if the trainer raises the rear axle, put a matching riser under the front wheel. A tilted bike rotates every angle in the photo by the same amount, and no software can undo that afterwards.

No trainer? Lean against a wall with a helper holding the bike upright, or ride slowly past a fixed camera — but a trainer is far more repeatable.

Place the camera directly to your side, at 90° to the bike, aimed at your hip. Height matters as much as angle: the lens should sit at about hip or top-tube height, not at ground level pointing up — a low camera foreshortens the legs and distorts the knee angle.

Stand the camera back far enough that the whole bike and rider fit in the frame with margin on every side. More distance flattens perspective distortion; use zoom rather than stepping closer. Line up with the hip: if you can see both shoulders or both hips clearly separated, you are not truly side-on.

Fit angles are read at specific crank positions, so pedal into position, hold it, and shoot. You need two photos: one with the camera-side crank at 6 o'clock (pedal at the very bottom — for knee flexion, hip, torso, elbow and shoulder angles) and one at 3 o'clock (forward and horizontal — for KOPS).

Hold your normal riding posture in both: hands where you actually ride (hoods, or TT extensions), foot flat in its usual pedalling attitude, looking ahead — not down at the pedal.

Wear tight-fitting kit: pose detection finds your hip, knee and ankle through lycra, but loose shorts or a flapping jacket hide the joints and shift every landmark. Dark clothing against a light, uncluttered background gives the cleanest detection.

Light the scene evenly — daylight or room lights are fine. Avoid shooting into a bright window behind you (silhouettes lose the joints) and avoid harsh single-side light that buries half your body in shadow.

If a measurement looks wrong, the photo is the first suspect. These are the failures that shift angles the most:

• Camera not perpendicular — shooting from slightly ahead or behind compresses limbs; even a few degrees off-axis changes the angles.
• Camera too low — ground-level shots pointing up distort the knee and hip angles.
• Tilted framing — the horizon in the photo must be level; a tilt of more than about 4° makes torso readings meaningless.
• Wrong crank position — knee flexion read anywhere but the true 6 o'clock reads too bent.
• Cropped rider — a cut-off foot or head means missing landmarks; keep the whole rider and bike in frame.
• Loose clothing hiding the hip or knee.

A single 2D photo contains no information about how the camera was aimed, so a tilt or off-axis error cannot be corrected after the fact — it can only be detected and rejected. Pedalyze checks each upload for tilt, off-axis perspective and cropping, and reports a photo as unusable rather than returning confident-looking numbers from a bad shot. If your photo is rejected, it is protecting your measurements, not being picky.

Portrait or landscape?

Either works — what matters is that the entire bike and rider fit in the frame with margin, and the camera is level. Landscape usually makes it easier to keep distance and get everything in.

Can I take the photos alone, without a helper?

Yes: put the phone on a tripod or shelf at hip height, use the self-timer or an interval-shooting mode, and pedal into position. Take several shots and keep the ones where the crank position is exact.

Which side of the bike should I photograph?

Either side works; the drivetrain side has the chainring near the crank but detection handles both. If you compare fits over time, always shoot the same side so the small left-right asymmetries every rider has do not masquerade as fit changes.

Do photos beat measuring with an app and a goniometer?

A good photo measured by pose detection is more repeatable than holding a goniometer against a rider, and it captures all the angles at once. The trade-off is that the photo itself becomes the instrument — which is why the setup on this page matters.

• Knee angle in bike fitting
• KOPS explained
• Road bike fit angles
• TT & triathlon bike fit

• Saddle height calculator — Estimate your saddle height from inseam with the LeMond method, measured from the bottom bracket to the top of the saddle.
• Bike frame size calculator — Get your frame size from your height and cycling inseam, for road, gravel, mountain and hybrid bikes, with a size chart for each.