Body Composition Calculators
These body composition calculators add what BMI leaves out: where weight sits on the body, a body fat estimate, the healthy weight range for one height and the energy a body uses at rest.
The simplest of these measures is the waist-to-height ratio: waist divided by height. It estimates fat around the middle of the body, which BMI cannot see.
The UK's NICE guideline classes a ratio of 0.4 to 0.49 as healthy and sums the advice up in one line: keep your waist to less than half your height. The waist-to-height ratio calculator shows all three NICE bands.
The same ratio is now an official standard. Since July 2026 the Army measures body composition with the waist-to-height ratio alone, with a limit of 0.55, under Army Directive 2026-13. Height and weight tables and the tape test that estimated body fat are no longer used.
The Army body fat calculator applies the Army's own measuring and rounding rules, which differ from the general calculator. It states when the rule was last checked against the directive (October 12, 2026).
Three more tools answer common follow-up questions. The body fat calculator estimates a body fat percentage from neck, waist and hip measurements with the U.S. Navy tape equations, and says how far off that estimate can be.
The ideal weight calculator shows the healthy weight range for a height next to the classic single-number formulas, and explains why the range is the better guide. The BMR calculator estimates resting energy with the Mifflin-St Jeor equation.
None of these tools measures body fat directly, and none gives a diagnosis. For weight against height alone, start with the BMI calculator.
All body composition calculators
- Army Body Fat CalculatorThe current Army standard: waist-to-height ratio below 0.55. Pass or fail with the Army's rounding rules.
- BMR CalculatorCalories your body uses at rest, from the Mifflin-St Jeor equation.
- 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.
- Waist-to-Height Ratio CalculatorWaist divided by height, with the NICE bands. Keep your waist below half your height.
Sources
- NICE guideline NG246: Identifying and assessing overweight, obesity and central adiposity — waist-to-height bands, lower BMI thresholds for some ethnic backgrounds, caution with BMI in older and muscular adults (checked October 12, 2026)
- Army Directive 2026-13 (Army Body Composition Program and Standards) — signed by the Secretary of the Army on 1 July 2026, effective immediately; listed as active by the Army Publishing Directorate (checked October 12, 2026)
- EXORD 182-26, Annex A: Implementing Guidance for Waist to Height Ratio Measurement Procedures for the ABCP — measurement and rounding rules, Figure B-1 (maximum waist by height), instructions for DA Form 5500 (checked October 12, 2026)