Knee Angle in Bike Fitting: Recommended Range and How to Measure
Updated · Written by Stas Bashylov, Ihor Twin
The knee angle at the bottom of the pedal stroke is the most common way to check a saddle height after you have set it with a formula. It responds to everything a formula ignores — your flexibility, foot position, cleats and shoes — so it tells you how the saddle height works for your body.
The catch: there are two widely used target ranges, and they come from different measuring methods. Mixing them up is the most common source of confusion.
What exactly is measured
The angle is measured with the crank at the bottom of the stroke (6 o’clock), using three points: hip (greater trochanter), knee (lateral knee joint) and ankle (lateral malleolus).
Bike fit ranges are usually given as knee flexion: how far the knee is bent away from a straight leg, where 0° means fully straight. Some tools instead show the interior angle between thigh and shin, where 180° means straight. The two are related simply:
interior angle = 180° − knee flexionRecommended knee angle ranges
| How it is measured | Knee flexion | Interior angle | Source |
|---|---|---|---|
| Static: sitting still, pedal held at the bottom | 25–35° | 145–155° | Holmes et al. (1994), as widely cited |
| Dynamic: filmed while pedalling | 30–40° | 140–150° | Ferrer-Roca et al. (2012) |
Static (Holmes). The 25–35° range is the figure later bike-fit literature attributes to Holmes, Pruitt and Whalen (1994), measured on a rider who is not pedalling, typically with a goniometer. The original paper’s full text is not openly available, and a few sources cite 25–30° instead, so treat it as the literature’s attribution rather than a verified quote.
Dynamic (Ferrer-Roca). Ferrer-Roca and colleagues measured knee flexion on 2D video while well-trained cyclists pedalled and treat 30–40° as the optimal range for that method. They also found that setting the saddle by inseam percentage alone did not reliably put riders inside this range.
How to measure your knee angle
With a phone
- Put the bike on a trainer and level it. Wear fitted clothing so your knee and hip are visible.
- Place the phone side-on, level, at roughly hip height and 2–3 m (7–10 ft) away, so the whole bike is in frame. Avoid wide-angle lenses.
- For a static check, stop with the near-side pedal at the bottom and sit naturally. For a dynamic check, record a short video while pedalling at your normal effort.
- Measure the angle between hip, knee and ankle — by hand on the photo, or automatically with the FitInspector position check.
FitInspector picks the range that matches how you captured: a single photo is compared with the static range, a video (or several photos across the pedal stroke) with the dynamic range. It also shows torso, shoulder and elbow angles. More on setup in how to check your cycling position at home.
What your reading means
- Less flexion than the range (leg straighter): the saddle is likely too high. Lower it by about 3–5 mm and re-check.
- More flexion than the range (knee more bent): the saddle is likely too low. Raise it by about 3–5 mm and re-check.
- Inside the range: a good sign. Fine-tune by feel; small differences within the range are personal.
To get a starting saddle height before you measure, use the saddle height guide or the bike fit calculator.
Frequently asked questions
What is the correct knee angle at the bottom of the pedal stroke?
Is a knee angle of 150 degrees good?
Sources
- Holmes JC, Pruitt AL, Whalen NJ. Lower extremity overuse in bicycling. Clin Sports Med. 1994;13(1):187–205. (25–35° range as cited in later literature; full text not verified.)
- Ferrer-Roca V, Roig A, Galilea P, García-López J. Influence of saddle height on lower limb kinematics in well-trained cyclists: static vs. dynamic evaluation in bike fitting. J Strength Cond Res. 2012;26(11):3025–3029. Link