Lorentz Formula Ideal Weight Calculator

About this calculator

The Lorentz formula refines the older Broca index for estimating ideal body weight, correcting for the fact that Broca’s simple height-in-cm-minus-100 rule overestimates ideal weight for taller people. For men: Ideal Weight (kg) = (Height - 100) - ((Height - 150) / 4); for women: Ideal Weight (kg) = (Height - 100) - ((Height - 150) / 2.5). Both formulas only apply meaningfully above 150 cm, which is exactly the range Lorentz was designed to correct.

Developed in the early 20th century, the Lorentz formula predates BMI as a clinical shorthand and is still referenced in some European medical and nutrition contexts as a quick sex-specific ideal weight estimate, particularly because it (unlike a flat BMI target) scales its correction with how tall someone is rather than applying one formula uniformly. It’s most useful as a rough reference point alongside — not a replacement for — BMI and body composition measures, since neither Broca nor Lorentz accounts for frame size or muscle mass.

This calculator takes your height and sex and returns your Lorentz ideal weight along with the BMI that weight corresponds to.