Cormic Index Calculator (Trunk-to-Leg Proportions)
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/10/2026
The Cormic index is calculated with (sitting height ÷ standing height) × 100. Most adults fall between 50 and 55: a lower value indicates long legs relative to the trunk, a higher value a long trunk relative to the legs.
Explanation
The Cormic index relates sitting height — measured from the seat to the top of the head, back straight — to standing height. It expresses in a single value how much of total stature is trunk, the rest being the lower limbs. It's a classic anthropometric measure: individual proportions like this influence relative ease on certain movements without determining anything definitively, in the same spirit as the strength benchmarks in our strength-to-weight ratio calculator. In strength training, a high Cormic index (long trunk, short legs) often goes together with a torso that stays more upright in the squat and a shorter range of motion in the deadlift, while a low index (long legs, short trunk) tends to force a more pronounced forward lean in the squat and mechanically favors the deadlift. Most adults fall between 50 and 55, with documented average differences by geographic origin. This calculator gives the ratio and a general tendency (trunk rather long, balanced, or rather short), without trying to slot the result into a precise anthropological category: what matters for adapting your technique is the direction of the deviation from the average, not a threshold to the tenth. Segment lengths also interact with ankle and hip mobility, pelvis width, and arm length, a set that no single index sums up — much as the balance between pressing and pulling strength, tracked by our push-pull strength ratio calculator, depends on more than one measurement.
Example: sitting height 90 cm, standing height 175 cm
Inputs
Sitting height: 90 cm. Standing height: 175 cm.
Calculation
Cormic index = (90 ÷ 175) × 100 ≈ 51.43.
Result
An index of 51.43 corresponds to balanced trunk-to-leg proportions, close to the common median value.
Frequently asked questions
How do I measure sitting height correctly?
Sitting on a flat, hard surface, back and head against a wall, legs at a right angle, feet flat: sitting height is the vertical distance between the seat surface and the highest point of the skull. Taking the measurement without shoes or a cushion, standing slightly tall as for a standing height measurement, gives a result comparable from one time to the next.
Is an "unfavorable" Cormic index for a movement a handicap?
No, it's a parameter to factor into technique, not a limit. A lifter with long legs can progress just fine in the squat by adjusting stance width, target depth, and possibly using heel-raised shoes; the index explains a sensation, it forbids no exercise.
Does this index have a use outside strength training?
Yes, the Cormic index is used in anthropology and ergonomics (sizing workstations, seats, cockpits), as well as in exercise physiology, where relative leg length influences, for example, running economy and the biomechanics of rowing or cycling.