Find body fat percentage for men, from BMI and age.
The Deurenberg equation, using the male-specific constant.
Men: 1.2 × BMI + 0.23 × age − 16.2
This calculator estimates a man's body fat percentage from his BMI and age using the Deurenberg equation: body fat % = 1.2 × BMI + 0.23 × age − 16.2. No tape measure, callipers or scanner is needed, which is its main appeal.
Body fat percentage says what share of body weight is fat. For men it is a more useful health and fitness indicator than weight alone, because two men with the same BMI can differ widely in how much of that weight is muscle. Gyms, corporate health camps and fitness apps often quote it.
Because the inputs are only BMI and age, the result is a population-average estimate. It is good for a rough picture and for tracking change, and weaker for athletes or anyone with an unusual build.
1. Work out BMI = weight (kg) ÷ height (m)², or take it from a BMI calculator.
2. Multiply BMI by 1.2.
3. Multiply age in years by 0.23.
4. Add the two results.
5. Subtract the male constant 16.2: body fat % = 1.2 × BMI + 0.23 × age − 16.2.
6. If the answer comes out below 0, treat it as 0; the formula is not meant for such low values.
7. Optionally find fat mass = weight × body fat % ÷ 100, and lean mass = weight − fat mass.
In 1991 Paul Deurenberg and colleagues measured body density in about 1,200 Dutch adults and children by underwater weighing, then converted density to body fat percentage. They regressed that fat percentage on BMI, age and sex. For adults the result was body fat % = 1.2 × BMI + 0.23 × age − 10.8 × sex − 5.4, where sex is 1 for men and 0 for women. For men the two constants combine to −16.2. The standard error was about 4 percentage points, so a result of 22% really means somewhere around 18% to 26% for most men.
At a fixed BMI, older men tend to carry more fat and less muscle than younger men. Muscle mass declines slowly from middle age, and fat, particularly around the abdomen, often takes its place without much change in weight. The 0.23 × age term captures this: ten extra years add 2.3 percentage points at the same BMI. It is an average trend, and an older man who trains regularly may be well below the estimate, while a sedentary younger man may be above it.
Since BMI counts muscle as if it were fat, the formula overestimates fat in muscular men, sometimes by 10 points or more. It is also known that South Asian adults tend to have a higher body fat percentage at the same BMI than the European group Deurenberg studied, so the formula may underestimate fat for many Indian men. Skinfold callipers, bioelectrical impedance scales and DEXA scans measure more directly. For tracking, use the same method each time, because switching methods adds its own error.
Imran is a 38-year-old sales manager in Hyderabad whose BMI from his annual health check is 26.4. He wants a quick body-fat estimate before a company fitness challenge.
Answer: Estimated body fat 24.2%
Treating the estimate as a measurement and comparing it directly with a DEXA or impedance reading.
Using it for bodybuilders or active sportsmen, where BMI mostly reflects muscle and the fat estimate is inflated.
Entering weight instead of BMI in the BMI field.
Using the formula for boys under 18; Deurenberg published a separate version for children.
Reading a small month-to-month change as meaningful when the formula's own error is around 4 percentage points.
Getting a rough body-fat figure when no scale or calliper is available.
Tracking the direction of change during a weight-loss programme using the same method each time.
Corporate wellness camps screening employees quickly from BMI and age.
Estimating lean body mass as an input to other nutrition formulas.
How accurate is this compared to a real body fat test?
It is an estimate based on large groups of people, not a direct measurement of you. Methods like DEXA scans or skinfold callipers give a more accurate result for you personally.