BMI and body fat calculators, with the working shown.
Every result comes with its formula, its category limits and the source they come from.
- Adults, 20 and over
- Use the calculator here, or open the BMI calculator for the formula and the healthy weight range.
- Children and teens, 2 to 19
- The kids BMI calculator gives the BMI-for-age percentile from the CDC growth charts.
- Soldiers and applicants
- The Army body fat calculator checks the standard in force since July 2026: a waist-to-height ratio below 0.55.
BMI categories for adults
Full BMI chart- UnderweightBMI below 18.5
- Healthy weightBMI 18.5 to 24.9
- OverweightBMI 25.0 to 29.9
- ObesityBMI 30.0 or above
The same cut-offs are used by WHO, CDC and the U.S. National Institutes of Health. BMI is a screening measure: it cannot tell muscle from fat, and it is not a diagnosis.
Can you calculate body fat from BMI?
Not directly: BMI uses only height and weight, so it cannot tell fat from muscle and bone. The body fat calculator estimates a body fat percentage from tape measurements of the neck and waist (women add hips) with the U.S. Navy equations, which can be off by 3 to 4 percentage points.
For BMI, the healthy weight range for adults is 18.5 to 24.9. Body fat charts differ from source to source, and we have not found one set of categories we can cite with confidence, so the body fat estimate comes without a grade. For a tape measurement with published bands, use the waist-to-height ratio calculator: NICE advises keeping your waist below half your height.
More BMI and body composition calculators
All tools- Reverse BMI CalculatorThe weight that matches a BMI at your height, in pounds, kilograms and stone.
- Waist-to-Height Ratio CalculatorWaist divided by height, with the NICE bands. Keep your waist below half your height.
- Body Fat CalculatorBody fat estimate from a tape measure with the U.S. Navy equations, and how far off it can be.
- Ideal Weight CalculatorHealthy weight range for your height, next to the Devine, Robinson and Hamwi formulas.
- BMR CalculatorCalories your body uses at rest, from the Mifflin-St Jeor equation.
- BMI ChartHeight and weight table with BMI and category, in pounds and kilograms, plus the healthy weight range for every height.
How BMI360 keeps the numbers right
- Children's percentiles are calculated from the data file CDC publishes, stored unchanged and checked by a test against CDC's own printed percentiles.
- The Army rule is kept in one dated file with links to the directive. The site will not build if that file has not been re-checked for 120 days.
- No named reviewer yet. Pages will name a medical reviewer only when a real, qualified person has checked them. Until then each page lists the sources it was built from.