Broca Index Ideal Weight Calculator

About this calculator

The Broca index, devised by 19th-century French surgeon Paul Broca, is one of the oldest formulas for estimating ideal body weight: start with height in centimetres minus 100, then apply a sex-based correction to that base figure — subtracting about 10% for men and about 15% for women reflects the average difference in body frame and composition between the sexes. A 175 cm man, for instance, starts from a base of 75 kg and lands around 67.5 kg after the correction.

Despite predating modern body-composition science by over a century, the Broca index remains popular for its simplicity — no scale, calipers or calculator beyond basic arithmetic are needed — and it is still referenced in some European clinical contexts alongside newer methods like BMI and the Hamwi or Devine formulas, though it does not account for frame size, muscle mass or age the way more modern indices attempt to.

This calculator takes your height and sex and returns your Broca index ideal weight with the correction already applied.