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Body Fat Calculator – Estimate Your Body Fat Percentage

Get a rough estimate of body fat percentage from age, height and weight. Choose metric or imperial units and see the BMI value used in the estimate.

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Estimated body fat percentage

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BMI used in the estimate

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This is a rough adult estimate based on BMI, not a direct body composition measurement or medical advice.

Runs in your browser – your data never leaves your device Also available via our free API

How to use the Body Fat Calculator

  1. 1 Choose metric or imperial units.
  2. 2 Enter your age, height and weight, then choose the sex coefficient used by the equation.
  3. 3 Read the estimated body fat percentage and the BMI used to calculate it.

What is body fat percentage?

Body fat percentage is the proportion of total body weight that is fat tissue. This calculator provides a rough estimate from body mass index (BMI), age and sex. It does not directly measure body composition.

How this body fat calculator works

The calculator uses the adult prediction equation published by Deurenberg and colleagues: body fat % = 1.2 × BMI + 0.23 × age − 10.8 × sex − 5.4, where the equation assigns 1 for men and 0 for women. BMI is calculated from height and weight. The original study developed and evaluated age- and sex-specific formulas for predicting body fat percentage from BMI (study on PubMed).

Because the estimate is based on BMI, it cannot distinguish fat mass from muscle, bone or other lean tissue. It can be less representative for very muscular people and may not fit every population equally well. The formula is a screening estimate, not a substitute for a body composition assessment.

How to interpret the estimate

Use the number as a rough point of reference and consider it alongside other information about your health. Methods such as a professionally administered body composition assessment use different measurements and can also have limitations. A single formula cannot account for all individual differences.

Intended for adults

This calculator is for general information for adults, not diagnosis or medical advice. It should not be used to assess children or teenagers. Ask a qualified healthcare professional about personal health concerns or the right way to assess body composition.

Frequently asked questions

How does this body fat calculator estimate body fat?

It applies an adult equation that estimates body fat percentage from BMI, age and sex. The result is a rough prediction, not a direct measurement.

What formula does the calculator use?

It uses the Deurenberg adult equation: 1.2 × BMI + 0.23 × age − 10.8 × sex − 5.4, with a sex coefficient of 1 for men and 0 for women.

How accurate is a BMI-based body fat estimate?

It can differ from an individual measurement because BMI does not distinguish muscle from fat and prediction error varies between people.

Can I use this calculator to assess a child?

No. This calculator uses an adult prediction equation and is intended for adults only.

Is this result medical advice?

No. It is a rough informational estimate, not a diagnosis or a replacement for guidance from a qualified healthcare professional.

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