How to Calculate BMI

The BMI formula

BMI divides weight in kilograms by height in metres squared. The squaring is what makes the index comparable across people of different heights.

• Metric: BMI = weight (kg) ÷ height (m)²
• Imperial: BMI = 703 × weight (lb) ÷ height (in)²
• Example: 72 kg at 1.75 m → 72 ÷ (1.75 × 1.75) = 23.5

The standard categories

These thresholds were designed for population-level screening. Some populations have different risk thresholds at the same BMI, and many health services adjust the ranges accordingly.

Where BMI is misleading

BMI treats all mass as equal. It cannot tell muscle from fat, and it says nothing about where fat is carried — which matters more for health risk than total mass.

• Muscular athletes often score in the "overweight" range with low body fat.
• Older adults can have a normal BMI while carrying excess fat and low muscle mass.
• Fat carried around the abdomen carries more metabolic risk than fat on the hips and thighs.
• BMI is not used on its own for children — age- and sex-specific growth charts are used instead.

Treat BMI as one signal among several. Waist circumference, blood pressure, blood lipids, fitness and how you feel all tell part of the story. Speak to a health professional before making significant changes.

Using BMI to set a weight range

You can rearrange the formula to find the weight range that puts you in the healthy band for your height: weight = BMI × height².

For a height of 1.75 m, the healthy band runs from 18.5 × 3.06 ≈ 56.7 kg to 24.9 × 3.06 ≈ 76.2 kg. The VELNARO BMI calculator shows this range automatically.