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Ponderal Index Calculator

Calculate Rohrer's Ponderal Index (weight ÷ height³) — a height-cubed alternative to BMI that's more reliable at very short or very tall heights — in metric or imperial units.

Ponderal index
13.06 kg/m³
Where this falls
Within the typical adult range (11-15)

How it works

The Ponderal Index (also called Rohrer's Index) is BMI's less common sibling: instead of dividing weight by height squared, it divides by height cubed — PI = weight(kg) ÷ height(m)³. Cubing height scales more like an actual body volume, which is why PI is often preferred over BMI at the extremes of height, where BMI tends to over-flag very tall people as overweight and under-flag very short people, and why it's the standard index used to assess newborns' size at birth relative to their length.

A commonly cited typical range for adults is roughly 11 to 15; this calculator reports where your result falls relative to that range, but — unlike BMI's WHO-defined cutoffs — this range is a general reference rather than a strict clinical diagnostic threshold.

Metric inputs are converted to kilograms and meters internally (the units that range is calibrated for) before the formula runs, so entering the exact same body size in imperial units returns the identical index.

FAQ

How is this different from BMI?

BMI divides weight by height squared (kg/m²); the Ponderal Index divides by height cubed (kg/m³). Because height is cubed instead of squared, PI scales more consistently with body volume across a wide range of heights, so it's less likely than BMI to misclassify someone who's unusually short or unusually tall.

Is the 11-15 range an official medical guideline?

No — unlike BMI's WHO-published cutoffs, there's no single internationally standardized banding for adult Ponderal Index. The 11-15 range is a widely cited general reference, not a diagnostic threshold, so treat the classification here as a rough orientation rather than a medical judgment.

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