Body composition calculator
Sitting height ratio calculator
How much of your height is leg and how much is torso — the Cormic index, and what it means for your squat and deadlift. Free, instant, no sign-up.
Inside the typical adult range
Proportions decide which lifts suit you. The coach builds the programme around them.
What is the sitting height ratio?
Sitting height divided by standing height, expressed as a percentage. It is also called the Cormic index, and it answers a question a single height measurement cannot: two people who are both 178 cm can differ by ten centimetres in where that height sits. One has a long torso and short legs, the other the reverse, and almost nothing else about them can be compared properly until you know which.
Why lifters care about this
Because limb proportions set the leverages you are working against, and no amount of training changes them. A long femur relative to your torso lengthens the moment arm in a squat: to keep the bar over midfoot you have to lean further forward, which loads the hips and back more and usually means a lower squat relative to your deadlift. A long torso does the opposite — a more upright squat, more quadriceps, and typically a squat that outpaces the deadlift. Neither is better. What it changes is which technique cues are worth chasing, which lift is likely to be your strong one, and whether the person whose form you are copying on video is built anything like you.
Why anthropometrists care about it
Because it is the main reason BMI is not comparable across populations. BMI puts height in the denominator without asking what the height is made of, and a body with relatively shorter legs has more mass packed into the same stature — so it reads heavier at identical body composition. Norgan's work in the 1990s showed that most of the gap in average BMI between population groups tracks the Cormic index rather than any difference in fatness. This is one of the reasons separate BMI cutoffs exist for some populations at all.
How to measure sitting height
Sit on a hard, flat surface of known height with your back against a wall, feet flat on the floor or supported, thighs horizontal. Sit up tall, look straight ahead, and have someone mark the wall at the top of your head. Measure from the seat surface to that mark — from the seat, not from the floor. That last point is where nearly every wrong answer comes from: measuring from the floor gives a number close to 70 % of standing height, and this calculator will refuse it rather than report a nonsense ratio.
What this is not
It is not a talent test, and it is not a reason to avoid a lift. Proportions shift the mechanics of a movement; they do not disqualify anyone from it, and there are world-class squatters with long femurs who simply squat differently. This page also asks nothing about ancestry on purpose. Population averages for the Cormic index differ by about two percentage points, while the spread between individuals within any population is several times that — so classifying yourself into a group would replace a measurement you have just taken with a worse estimate.