Body Fat Percentage Calculator
Estimate your body fat percentage, body fat mass and lean body mass from basic body measurements.
Calculate Body Fat Percentage
Enter your age, sex, height, weight and waist measurement to get an estimate.
What Is Body Fat Percentage?
Body fat percentage represents the estimated proportion of your total body weight that consists of fat. Unlike body weight alone, it attempts to distinguish fat mass from the rest of the body's mass.
Body composition can be useful when tracking changes over time, because body weight can change for many reasons, including changes in muscle, water and fat.
How to Use This Body Fat Calculator
- Select your sex.
- Enter your age.
- Choose metric or imperial measurements.
- Enter your height and weight.
- Measure and enter your waist circumference.
- Select Calculate Body Fat.
How the Estimate Is Calculated
This calculator uses the Relative Fat Mass (RFM) approach, which estimates body fat percentage using height, waist circumference and sex.
Body Fat % = 64 − 20 × (height ÷ waist)
For females:
Body Fat % = 76 − 20 × (height ÷ waist)
Height and waist are converted to the same unit before the calculation. The calculator also uses your weight to estimate body fat mass and lean body mass.
Example Calculation
Height: 175 cm
Waist: 85 cm
Body Fat % = 64 − 20 × (175 ÷ 85)
Body Fat % ≈ 22.8%
The example demonstrates how the height-to-waist relationship is used in the RFM equation. The result should be interpreted as an estimate rather than an exact body-fat measurement.
Body Fat Mass and Lean Body Mass
Body Fat Mass
Estimated body weight represented by the calculated body fat percentage.
Lean Body Mass
An estimate of body weight remaining after subtracting estimated fat mass.
BMI
A separate height-and-weight index shown alongside the body fat estimate for additional context.
Why Waist Measurement Matters
Waist circumference provides information about body size that is not captured by weight alone. The RFM method combines waist circumference with height to produce an estimate of body fat percentage.
For consistency, measure your waist in the same location and under similar conditions when comparing measurements over time.
Common Mistakes
- Using height and waist measurements in different units.
- Measuring the waist inconsistently between different measurements.
- Entering an incorrect sex because the calculator uses different equations for males and females.
- Treating the estimated percentage as a precise measurement.
- Comparing results obtained with different measurement methods as though they were directly interchangeable.
Understanding Body Fat Estimates
Body fat percentage varies naturally between individuals. Age, sex, body composition, genetics, activity and other factors can influence body composition.
A calculator is most useful for observing general trends when measurements are collected consistently rather than focusing on a single calculated number.
Important Limitations
Mathematical body-fat formulas can differ from measurements obtained with professional body-composition methods. The result should not be treated as a diagnosis or medical assessment.
This tool is intended for general informational and educational purposes. It is not a substitute for individualized medical, nutritional or fitness advice. If you have health or body-composition concerns, consult an appropriately qualified healthcare professional.
Frequently Asked Questions
What is body fat percentage?
Body fat percentage is the estimated percentage of total body weight represented by fat mass.
How does this calculator estimate body fat?
It uses the Relative Fat Mass method, which uses height, waist circumference and sex to estimate body fat percentage.
Do I need my waist measurement?
Yes. The RFM method used by this calculator requires both height and waist circumference.
Is the result accurate?
The result is an estimate and can differ from actual body composition. Consistent measurements are more useful for observing changes over time.
What is lean body mass?
Lean body mass is the estimated portion of body weight remaining after subtracting estimated body fat mass.
Can body fat percentage change without major weight changes?
Yes. Changes in fat mass, muscle mass and other components of body composition can occur even when overall body weight changes only slightly.
Should I use this calculator for medical decisions?
No. The calculator is intended for general information and should not replace professional medical or nutritional assessment.
Related Tools
Check Your Body Fat Estimate
Enter your measurements above to calculate an estimated body fat percentage, body fat mass and lean body mass.
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