Check if you have a short or long torso: enter standing and sitting height in cm or inches to get your Cormic Index and an estimated torso type.

Compares sitting height (seat to crown) with standing height.

Measure upright without shoes.

Sit upright on a firm surface. Measure vertically from the seat surface to the top of the head.

Optional settings

Related Calculators

Sitting Height Ratio Formula (Cormic Index)

The sitting-height ratio, also called the Cormic Index, describes sitting height relative to standing height. Sitting height includes the head and neck, so it is different from anatomical trunk length, garment back length and backpack torso length.

Sitting Height Ratio = Sitting Height / Total Height

Multiply the sitting-height ratio by 100 to express the Cormic Index as a percentage: 0.52 is 52%. The calculator labels a Cormic Index below 51% as a short torso, 51–52.9% as average and 53% or more as long, a general adult scale. For example, 90 cm sitting height divided by 175 cm standing height is approximately 0.5143, or 51.43%. The other input method uses subischial leg length = standing height − sitting height; do not substitute clothing inseam or floor-to-chair height.

Population Averages by Ancestry

Reference averages describe the particular sample, ages and measurement protocol in a study. They do not determine an individual’s proportions from ancestry. Compare a measurement only with an appropriate reference dataset; this calculator does not assign population averages or infer ancestry.

Sex and Age Differences

Reference charts may differ by age and sex. A sex-specific reference describes its study sample and does not establish a universal ideal or a clothing-size rule. The calculator’s short, average and long labels use one general adult scale, not a sex-specific band.

Sitting-height proportions change during growth. Children require age-appropriate reference charts, and a single adult cutoff should not be applied throughout childhood. Clinical interpretation also considers stature and measurement technique.

How to Measure Sitting Height Accurately

Measure standing height upright without shoes. For sitting height, sit as erect as possible on a firm, level seat with the head level and gaze straight ahead. Measure vertically from the sitting surface to the crown of the head, excluding the seat height. Repeat using the same technique. Do not use a cushion, clothing inseam or floor-to-chair height as sitting height.

Torso Proportions and Strength Training

This calculator does not measure femur length, tibia length, arm length or joint movement. Its head-inclusive sitting-height ratio should not be treated as a direct measure of lifting leverage, lumbar loading or the squat technique suitable for an individual.

The result alone cannot select conventional versus sumo deadlift stance or predict lifting performance. Percentages based on a study’s anatomical torso segment are not interchangeable with the head-inclusive sitting-height percentage calculated here.

Clothing Fit and Torso Proportions

Garment fit depends on the measurements and pattern of the particular item. Use the brand’s specified back length, rise, circumference and other fit measurements. Cormic Index is not a garment size, natural-waist location or a rule about which styles someone should wear.

Backpack and Gear Sizing

Backpack torso length is different from sitting height. Follow the manufacturer’s method: Osprey, for example, measures from the C7 vertebra at the base of the neck to the iliac crest at the top of the hips. Use the size chart and adjustment range for the specific pack; this calculator does not convert Cormic Index into a pack size.

Ergonomics and Seated Design

Sitting height can inform seated head-clearance measurements, but this ratio alone does not specify seat-pan depth, reach, eye height or a workspace configuration. Measure the dimensions relevant to the person and task rather than choosing equipment from a universal torso label.

Clinical Significance

Clinicians may compare sitting height and standing height with appropriate reference charts when assessing disproportionate growth. Original reference studies use age-, sex- and population-specific data and consider stature. This calculator supplies a proportion only; it does not diagnose a growth disorder, identify disease, or estimate lung function.

Sport-Specific Advantages

This calculator does not predict sport performance or identify an ideal body type. Sitting-height ratio alone does not measure the limb segments, arm span, mobility, strength or technique involved in an activity. Interpret sport-specific research using the measurements and population actually studied.