Body Mass Index is defined in SI units as weight (kg) / height
(m)², so the kg/cm form is the most direct — the calculator
divides your weight by your height in metres squared with no unit
conversion. The metric form is the default everywhere outside the
United States, and it is the form most clinical guidelines use.
How the calculation works
For a 70 kg person who is 170 cm tall, BMI = 70 ÷ (1.70 × 1.70) = 70 ÷ 2.89 = 24.22 — comfortably inside the WHO healthy band of 18.5–24.9. The kg/cm form avoids the 703 factor used in the imperial version, and the result is the same number to one decimal place either way.
Switching units mid-calculation
You can type your numbers in kg and cm, then switch to lb/ft+in or kg+ft/in without re-typing — the calculator carries your values across the unit swap. This is useful if you weigh yourself on a metric scale but report your height in feet and inches (or vice versa).
Reading the result
The gauge shows your BMI against the four WHO bands. Underneath, you'll see BMI Prime (BMI / 25), Ponderal Index, body-fat percentage, healthy weight range (kg), ideal weight (Devine, kg), lean body mass (Boer, kg), BMR and TDEE. Use the activity buttons to switch between sedentary, light, moderate, active and very active multipliers.
Next steps
- Metric BMI calculator (this page in different form)
- BMI calculator in lb and inches
- BMI calculator in kg and feet/inches
- Imperial BMI calculator
- Asian BMI calculator for ≥23 / ≥27.5 cut-offs