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Deurenberg Body Fat Calculator

Get a body fat estimate without calipers, using just BMI, age and sex.

How it is calculated

First the tool computes BMI: BMI = weight ÷ (height ÷ 100)² with weight in kilograms and height in centimetres. Then it applies BF% = 1.20 × BMI + 0.23 × age − 10.8 × S − 5.4, where age is in years and S is 1 for male and 0 for anything else, so only the choice “male” takes off the 10.8 points. Fat mass is BF% × weight ÷ 100 in kg. Weight and height must be above zero. There is no age check and no lower or upper limit on the result, so an implausible input can produce a very low or even negative percentage. The result is a statistical estimate from BMI, not a measurement of your body composition.

Worked example

A 35-year-old woman, 65 kg and 165 cm. Height in metres is 1.65, so BMI = 65 ÷ 2.7225 = 23.88. Body fat = 1.20 × 23.88 + 0.23 × 35 − 0 − 5.4 = 28.65 + 8.05 − 5.4 = 31.30%. Fat mass = 31.30% × 65 kg = 20.35 kg. The same weight, height and age entered as male give 20.50%, because the male term subtracts 10.8 points.

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Common mistakes

  • Entering height in metres (1.65) or weight in pounds. The fields take centimetres and kilograms, and a wrong unit changes the BMI and the whole result.
  • Treating the result as a measured value. It is estimated from BMI, so a muscular person with a high BMI will be shown with more fat than they really have.
  • Choosing the wrong sex option. The formula subtracts 10.8 points for male, so the choice shifts the answer by about 11 percentage points.
  • Comparing it with a DEXA, calliper or smart-scale reading and expecting a match. Different methods can differ by several points, so compare only values from the same method over time.

Sources

About this calculator

The Deurenberg formula estimates body fat percentage using just Body Mass Index, age, and sex — no calipers, scans, or specialized equipment required — making it a practical alternative to more invasive body composition measurement methods. The formula, published by Deurenberg and colleagues in 1991, is: Body Fat % = (1.20 × BMI) + (0.23 × Age) − (10.8 × sex) − 5.4, where sex is entered as 1 for male and 0 for female.

Because the formula relies on BMI, it inherits BMI’s known limitation of not distinguishing muscle mass from fat mass, so it can overestimate body fat in very muscular individuals and underestimate it in those with low muscle mass, and its accuracy was derived from and validated primarily on adult populations. It remains useful as a quick population-level or general estimate, but is not considered as precise as DEXA scans, hydrostatic weighing, or bioelectrical impedance analysis for individual clinical decisions.

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  • Editorial team

    The formula estimates body fat from BMI, age and sex, not from anything measured on your body, so a muscular person can read high and someone with little muscle can read low. It is most useful as a trend: keep the inputs consistent and watch the change. For a firmer number, compare with a skinfold or scan result. What measurement method do you trust?

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