Body Fat Calculator From BMI (Deurenberg)
No tape, no caliper — just height, weight, age and sex. This is the least accurate method; use it only when you have nothing to measure with.
How the From BMI method works
BMI = weight(kg) ÷ height(m)². Body fat % = 1.20 × BMI + 0.23 × age − 10.8 × (1 if male, 0 if female) − 5.4.
Worked example
A 30-year-old man with a BMI of 25: 1.20 × 25 + 0.23 × 30 − 10.8 − 5.4 = 20.7%. A woman with the same BMI and age: 31.5%.
Body-fat ranges (adults)
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Above average | 25%+ | 32%+ |
Other ways to estimate body fat
- U.S. Navy method — tape measure only, the quickest.
- Skinfold, 3-site — Three caliper pinches. The Jackson-Pollock generalised equation.
- Skinfold, 7-site — Seven caliper pinches — the most precise field method.
- RFM — Relative Fat Mass — one ratio of height to waist, no caliper.
Whichever you pick, stick with it: the direction over weeks matters more than the exact figure. To lower body fat, run a modest deficit with the calorie calculator, keep protein high via the macro calculator, and lift.
Source: Deurenberg, Weststrate & Seidell 1991. Siri body-density conversion: Siri 1961.
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Frequently asked questions
How does the BMI method work?
Why is it the least accurate method?
When is it still useful?
Does it need a children's version?
My lifting friend and I have the same BMI but different real body fat — which does this show?
Last reviewed: September 2026. Figures and formulas are checked against their published sources; see the site's data notes.