Ideal Body Weight Calculator

The formula this calculator uses

IBW = base + increment x (height in inches - 60)

base

Sex constant — 50 kg for men, 45.5 kg for women under Devine

increment

Weight added per inch above five feet — 2.3 kg under Devine, 1.9 kg under Robinson

height in inches

Metric heights must be divided by 2.54 before use

IBW

The estimated reference weight the formula returns

How to check the result by hand

1. 1

   Convert the height to inches

   The formulas count inches, so a metric height must be divided by 2.54 first. A height of 175 cm becomes 175 / 2.54 = 68.8976378 inches. Skipping this step and inserting 175 directly is the error that makes a metric result nonsensical.

2. 2

   Subtract the five-foot base

   Five feet is 60 inches, and the formulas measure only the excess above it. Here 68.8976378 - 60 = 8.8976378 inches. For anyone shorter than five feet the term is negative, which is why many versions clamp it to zero rather than returning a weight below the base constant.

3. 3

   Choose the formula and its sex constant

   Devine uses 50 kg for men and 45.5 kg for women with a 2.3 kg increment; Robinson uses 52 kg and 49 kg with 1.9 kg. Decide which one you are following and stay with it, because the constants are not interchangeable between the two.

4. 4

   Multiply and add

   Devine for a 175 cm man is 50 + 2.3 x 8.8976378 = 70.4645669 kg. The female version of the same formula is 45.5 + 2.3 x 8.8976378 = 65.9645669 kg. The multiplication always applies to the inches above five feet, never to the full height.

5. 5

   Compare against a range, not a point

   Put the single figure next to a BMI band before drawing any conclusion. At 175 cm that band is 56.65625 to 76.5625 kg, so the formula's answer sits inside a much wider interval of weights that are equally unremarkable. The range is the part that carries information about health.