How to Calculate BMI at Home (Step by Step)

With a bathroom scale and a tape measure, you can work out your Body Mass Index in under a minute — no app required.

The BMI formula

BMI = weight (kg) ÷ height (m)². In pounds and inches, multiply the result by 703.

Worked example (metric)

72 kg, 1.70 m. Square the height: 1.70 × 1.70 = 2.89. Divide: 72 ÷ 2.89 = 24.9 — top of "normal weight".

What your result means

The WHO adult ranges: under 18.5 (underweight), 18.5–24.9 (normal), 25–29.9 (overweight), 30+ (obese). BMI is a screening tool, not a diagnosis — muscular athletes often score high without being overweight.

Skip the maths? Use our BMI Calculator — it handles metric and imperial.