When to use this calculator
Estimate adult body fat percentage using the BMI-based Deurenberg equation, age and sex coefficient. A population estimate, not a body-fat measurement. Limited here to BMI 13.9–40.9 and ages 20–83. The original adult equation reported substantial individual prediction error and can overestimate in obesity. Not suitable for pregnancy, children or clinical decisions. No health category is assigned.
Explore the adult body measurements calculators for other questions in this topic. For a related calculation, use the BMR Calculator: Estimate adult resting energy expenditure using the simplified Mifflin–St Jeor equation.
This method does not use tape measurements
This calculator uses the BMI-based Deurenberg equation rather than a circumference or skinfold method. Changing the method can change the estimate because the input measurements and reference populations differ. The output is not a direct measurement of fat mass and cannot distinguish unusual body composition reliably.
PUTTING IT INTO PRACTICE
Body Fat Percentage: a worked example
The values below are an illustrative example, not a recommendation. Replace them with measurements or assumptions that match your question.
| Input | Example value |
|---|---|
| Age in years (integer) | 30 |
| Weight (kg) | 70 |
| Height (cm) | 175 |
| Equation sex coefficient | 1 |
| Result | 18.128571 % |
- Check the input labels and enter the example values above.
- Apply the relationship: BMI = kg/m²; estimated fat % = 1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4..
- The result is 18.128571 %, rounded for display.
How to interpret your result
A population estimate, not a body-fat measurement. Limited here to BMI 13.9–40.9 and ages 20–83. The original adult equation reported substantial individual prediction error and can overestimate in obesity. Not suitable for pregnancy, children or clinical decisions. No health category is assigned.
These tools are for adults aged at least twenty. BMI relates body mass to squared height and does not directly measure body fat, fitness, nutrition or individual health. It is an informational screening measure rather than a diagnosis.
Frequently asked questions
Why can this disagree with a body-composition scale?
A scale, circumference equation and BMI equation use different assumptions. Individual prediction error and measurement conditions can cause differences; agreement does not establish clinical accuracy.
Can BMI measure body composition?
No. BMI uses only mass and height. It does not distinguish muscle, fat, bone or fluid and cannot replace an individual health assessment.
When is the body fat percentage calculator useful?
Estimate adult body fat percentage using the BMI-based Deurenberg equation, age and sex coefficient. A population estimate, not a body-fat measurement. Limited here to BMI 13.9–40.9 and ages 20–83. The original adult equation reported substantial individual prediction error and can overestimate in obesity. Not suitable for pregnancy, children or clinical decisions. No health category is assigned.
How do I use the body fat percentage calculator?
Enter age in years (integer), weight (kg), height (cm), equation sex coefficient. The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
BMI = kg/m²; estimated fat % = 1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4..
What should I check before using the result?
A population estimate, not a body-fat measurement. Limited here to BMI 13.9–40.9 and ages 20–83. The original adult equation reported substantial individual prediction error and can overestimate in obesity. Not suitable for pregnancy, children or clinical decisions. No health category is assigned.
How are results rounded?
Scalar numbers display up to six decimal places, with scientific notation for very large or small values. Text, fraction, date and schedule outputs use the format described on the tool. Intermediate calculations use JavaScript floating-point arithmetic. Keep sensible precision for your measurements.
Further reading
For background on this topic, see Deurenberg et al.: original body-fat prediction study ↗. This is a topic reference, not an external review or endorsement of this tool.
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