How to Calculate BMI Step by Step

Body Mass Index compares your weight to your height squared. The calculation takes under a minute once you have accurate measurements.

Step-by-step

1. Measure weight on a calibrated scale, ideally in the morning before eating.
2. Measure height barefoot against a wall, or use a recent clinical measurement.
3. For metric: divide weight in kilograms by height in meters squared.
4. For imperial: multiply weight in pounds by 703, then divide by height in inches squared.
5. Compare your result to WHO adult categories: under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, 30+ obesity.
6. Use our BMI Calculator to verify and see the category label instantly.

Tips and common mistakes

• Round height to the nearest centimeter for consistency.
• BMI does not account for muscle mass — athletes may read 'overweight' despite low body fat.
• Pair BMI with waist circumference for cardiovascular risk screening.

Open the BMI Calculator to apply these steps with your own numbers instantly.

Frequently asked questions