BMI calculator
This free BMI (body mass index) calculator gauges the ratio of your weight to your height and shows which category the result falls into. Enter your weight (kg) and height (cm) and you'll immediately see the index and the category (underweight, normal, overweight, obese).
How the calculation works
The BMI formula is weight (kg) / height² (in metres). To convert height to metres, divide centimetres by 100. WHO classification: below 18.5 is underweight, 18.5–24.9 is normal, 25–29.9 is overweight, 30 and above is obese. BMI is a general indicator and doesn't account for muscle mass.
Worked example
For 70 kg and 175 cm, BMI = 70 / (1.75)² ≈ 22.9 — normal. At the same weight with 160 cm you'd get ~27.3 — overweight.
Frequently asked questions
What BMI is normal?
A value between 18.5 and 24.9 is considered normal.
Is BMI accurate?
It's a general indicator and ignores muscle, age and sex. Consult a doctor.
What units are used?
Weight in kilograms (kg), height in centimetres (cm).
Is the tool free?
Yes — completely free.