BMI Calculator
Your body mass index from your height and weight, and the WHO band it falls in.
Result…
How it's calculated
BMI = weight (kg) ÷ height (m)² Imperial: BMI = 703.07 × weight (lb) ÷ height (in)² WHO bands: under 18.5 underweight · 18.5–24.9 healthy · 25–29.9 overweight · 30+ obese
BMI compares weight with height and sorts adults into the World Health Organization bands. It is a quick screen for populations, not a diagnosis: it cannot tell muscle from fat, so athletes can read high, and it is not used for children (who use age percentiles) or in pregnancy.
Your numbers, step by step
About the BMI calculator
Body mass index (BMI) compares your weight with your height to give a single number. The number places adults in one of the World Health Organization weight bands. This calculator works in metric (kilograms and centimetres) or imperial (pounds, feet and inches) and shows the band your result falls in. BMI is a quick screening tool, not a diagnosis. Read the notes below before drawing conclusions from it.
How to use it
- Choose Metric or Imperial under Units.
- Enter your weight, then your height (feet and inches separately in imperial).
- Read your BMI and its WHO band in the result.
- Change either number to see how the band shifts; the steps show the sum with your values.
Worked example
An adult who weighs 70 kg and is 175 cm (1.75 m) tall has a BMI of 70 ÷ 1.75² = 70 ÷ 3.0625 ≈ 22.9. That is inside the 18.5–24.9 healthy-weight band.
Updated
Questions people ask
How is BMI calculated?
BMI is your weight in kilograms divided by your height in metres squared. In imperial units it is 703.07 × weight in pounds ÷ height in inches squared.
What is a healthy BMI for adults?
The WHO bands are: under 18.5 underweight, 18.5 to 24.9 healthy weight, 25 to 29.9 overweight, and 30 or more obese.
Is BMI accurate for athletes?
Not always. BMI cannot tell muscle from fat, so people with a lot of muscle can read as overweight while carrying little body fat.
Can children use this BMI calculator?
No. Children and teenagers are assessed with BMI-for-age percentiles that account for growth, not with the adult bands shown here.
Should I use BMI during pregnancy?
No. BMI is not meaningful during pregnancy. Ask a midwife or doctor about healthy weight gain instead.