Body fat percentage tells you more about body composition than weight or BMI alone. Two people of identical weight can have a completely different proportion of fat and muscle. In this guide we show the most popular methods for estimating fat percentage and the norms worth referring to.
Why is BMI alone not enough?
BMI does not distinguish fat from muscle. A muscular athlete and a person with excess body fat can have the same BMI even though their body composition is extremely different. That is why body fat percentage is helpful for assessing physique and metabolic health.
Measurement methods
- Calipers: measure the thickness of skin folds at several points on the body. Cheap and widespread, but accuracy depends on measurement technique.
- Bioimpedance analysis (BIA): scales and devices that pass a weak current through the body. The result depends on hydration, so it is worth taking the measurement under similar conditions each time.
- Estimation formula from BMI: lets you estimate fat percentage based on BMI, age and sex, without any special equipment.
The Deurenberg formula
A popular estimation formula takes the form: fat percentage = 1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4, where for sex we substitute 1 for men and 0 for women. It is an approximate method, but sufficient for tracking changes over time.
Worked example
Take a woman aged 30 with a BMI of 24:
- 1.20 × 24 = 28.8
- 0.23 × 30 = 6.9
- 10.8 × 0 = 0 (female)
- We add it up: 28.8 + 6.9 − 0 − 5.4 = 30.3 percent
A result of around 30 percent falls within the healthy range for a woman of this age.
Body fat percentage norms
The approximate ranges differ for women and men, because women naturally have a higher proportion of fat:
- Women: athletes 14–20 percent, good fitness 21–24 percent, healthy 25–31 percent, excess above 32 percent.
- Men: athletes 6–13 percent, good fitness 14–17 percent, healthy 18–24 percent, excess above 25 percent.
How to interpret the result?
A single measurement is best treated as a reference point. Observing the trend has greater value — whether the fat percentage is rising, falling or stabilising during training and dieting. Estimation formulas can be off by several percentage points, so it is best always to use the same method.
The methods and norms presented here are approximate and do not replace medical or dietary consultation. If you have concerns about your metabolic health, consult a specialist.
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