Saddle height calculator: how high should your bike seat be?

How to measure your inseam for a bike

Your cycling inseam is not your trouser leg length. It is the height from the floor to your crotch bone, and the book trick measures it well:

1. Take your shoes off and stand with your back to a wall, feet about 15 cm (6 in) apart.
2. Pull a hardback book up between your legs, spine up and level, as firmly as a saddle would press.
3. Have a helper mark the wall at the top of the spine (or hold the book and mark it yourself), then measure from the floor to the mark. Do it twice; if the readings differ, average them.

The methods, side by side

Saddle height has been studied for more than half a century, and the published methods agree on the broad answer while differing in detail. A 2011 review in Sports Medicine by Bini, Hume and Croft reviewed 62 references and found that the methods are inconsistent and not well validated, and that evidence on injury is limited. The authors suggested the knee-angle method, with the knee bent 25–30°, as a reasonable setting for reducing knee injury risk and oxygen cost. That is why this page gives you a number and a check.

Method	What you measure	Where it comes from
109% of inseam	Pedal spindle (crank at the bottom) to the top of the saddle = 1.09 × inseam	Hamley and Thomas, 1967, from ergometer studies; still widely used as a starting point
Knee angle 25–35°	Knee bend at the bottom of the stroke, from a side view	Holmes, Pruitt and Whalen, 1994, for preventing overuse injuries
Knee angle 25–30°	The same angle, a narrower band	Bini, Hume and Croft’s 2011 review
Heel method	Heel on the pedal at the bottom, leg straight	A quick traditional check, named in the same review

In a 2008 study, Peveler compared saddles set at 109% of inseam with saddles set by knee angle. Oxygen use was lower at a 25° knee angle than at 35° or at 109%, and he concluded that 25° suited both performance and injury prevention. In practice, 109% gets you close and the knee angle fine-tunes it. The review also lists LeMond’s inseam method; we haven’t included its multiplier because we couldn’t check it against the original book.

Turning 109% into a number you can measure

Fitters usually quote saddle height from the centre of the bottom bracket to the top of the saddle, along the seat tube. Turn the crank so it lines up with the seat tube, and the pedal spindle sits exactly one crank length further along the same line. So the bottom-bracket figure is 1.09 × inseam − crank length. For 820 mm and 172.5 mm cranks: 893.8 − 172.5 = 721.3 mm.

Checking your knee angle

1. Put the bike on a turbo trainer or lean it against a wall, level, and sit on it in your cycling shoes and shorts.
2. Pedal for a minute, then stop with the crank pointing straight down along the seat tube, your foot as it normally sits on the pedal.
3. Have someone photograph you from the side at hip height. Mark the hip bone, the centre of the outside of the knee and the outer ankle bone.
4. Measure the angle between the two lines with a protractor or a free photo app. The knee angle is 180° minus the inside angle at the knee. Enter it in the calculator.

Setback: why sliding the saddle changes its height

A seat tube leans back at an angle, often around 73° from horizontal (your bike’s geometry chart gives the exact figure). Moving the saddle along its rails therefore changes its distance from the bottom bracket, not just its position over the pedals. The calculator works it out exactly: with a 721 mm saddle height on a 73° seat tube, sliding the saddle 10 mm back puts it about 3 mm further from the bottom bracket, so lower the seatpost by about 3 mm to keep the same leg extension. Sliding forward does the opposite. Change height or setback, not both at once, so you can tell which one helped.

Adjusting your saddle safely

• Mark the seatpost with tape before you start, so you can always go back.
• Move it a few millimetres at a time and ride for a few days before changing again.
• Never raise the post above the minimum-insertion mark printed on it, and tighten the clamp to the torque printed on it or in the manual (carbon frames and posts especially).
• New shoes, cleats, pedals or a different saddle shape change the effective height, so re-check after any of them.

Common mistakes

• Measuring inseam with shoes on, or reading the trouser label: both add centimetres.
• Setting the saddle from frame size: two riders on the same frame can need very different heights.
• Copying a professional’s position: their height suits their flexibility and hours on the bike.
• Raising a long-time low saddle in one go: your muscles are used to the old position, so go in steps.
• Judging by toe-reach: if your toes point down to reach the bottom of the stroke, or your hips rock, the saddle is too high.

When to see a bike fitter or a physiotherapist

A calculator gets you into the right range; it can’t see how you move. See a professional bike fitter if you still feel uncomfortable after a few careful adjustments, if you ride long distances, or if your legs differ in length. See a doctor or a physiotherapist (physical therapist in the US) if you have pain that lasts after riding, swelling, numbness or tingling, or pain that keeps coming back. Knee pain has many causes besides saddle height, and a low saddle is only one of them: the Bini review found that the force on the kneecap joint appears to fall as the saddle rises. This page is general information, not medical advice.

Training as well as fitting? Zigzag Pulse works out heart-rate zones, and once the saddle is right, the gear calculator shows what each gear will feel like at your favourite cadence.