Input Parameters
Example data table
The following example values show typical outputs for different profiles. Actual results from the calculator will vary depending on your measurements.
| Example | Gender | Age (years) | Height (cm) | Weight (kg) | Method | Body fat (%) | Fat mass (kg) | Lean mass (kg) |
|---|---|---|---|---|---|---|---|---|
| Recreational athlete | Male | 28 | 178 | 78 | US Navy | 14 | 10.9 | 67.1 |
| Desk job worker | Female | 35 | 165 | 70 | BMI-based | 30 | 21.0 | 49.0 |
| Strength trainee | Male | 40 | 182 | 92 | Direct BF% | 18 | 16.6 | 75.4 |
Formulas used in this calculator
The calculator estimates body fat percentage using one of three options: the US Navy circumference method, the BMI-based Deurenberg equation, or a body fat percentage you already know.
US Navy circumference method
The US Navy method uses height and circumferences to estimate body density, which is then converted to body fat percentage. All entered circumferences in centimetres are converted to inches inside the formula.
- Men: Body fat % = 495 / (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450
- Women: Body fat % = 495 / (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450
In these formulas, height, waist, neck, and hip are in inches, so the calculator converts from centimetres before applying the equations.
BMI-based Deurenberg equation
When you select the BMI-based method, the calculator first computes body mass index using height in metres and weight in kilograms: BMI = weight / height².
The Deurenberg equation then estimates body fat percentage: Body fat % = 1.20 × BMI + 0.23 × age − 10.8 × sex − 5.4, where sex = 1 for men and 0 for women.
Direct body fat percentage
If you already know your body fat percentage from a reliable test (such as DEXA, calipers, or bioimpedance), you can enter it directly.
Body fat mass and lean body mass
Once body fat percentage is known, the calculator derives body fat mass and lean body mass as:
- Body fat mass (kg) = body weight × body fat % / 100
- Lean body mass (kg) = body weight − body fat mass
These equations are widely used in sports science and clinical nutrition. Values are still estimates and may differ from imaging based methods.
How to use this calculator
- Select your gender and enter your age in years.
- Enter height in centimetres and body weight in kilograms.
- Choose the estimation method that matches the data you have available.
- For the US Navy method, provide waist, neck, and hip circumferences as required.
- If you select the BMI-based method, only height, weight, age, and gender are needed.
- If you already know your body fat percentage, choose the direct option and enter that value.
- Click “Calculate body fat mass” to generate your results and automatically add them to the history table.
- Use the CSV button to download a spreadsheet of your results, or the print button to save the page as a PDF.
For best accuracy, take circumference measurements in the morning and repeat them consistently under similar conditions over time.
Related concepts and extended use
Tracking changes in body fat mass
Recording regular measurements lets you see whether training or nutrition plans are shifting fat mass or only total weight. The history table helps compare sessions and highlight meaningful, long term composition changes.
Comparing fat mass with energy calculations
Estimated fat mass can be combined with energetic calculations when you plan long term diet strategies. For advanced molecular perspectives, you may also explore the J to J/mol calculator.
Linking composition data to molecular amounts
When designing experiments or educational examples, it is sometimes useful to relate macroscopic mass to particle counts. You can combine this body fat mass output with the mole to atom calculator.
Comparing fat mass with atomic scale mass
Body fat mass exists on the kilogram scale, while chemistry often works with tiny quantities. To emphasise this contrast in teaching, connect this tool with the mass of atom calculator.
Using composition results in nutrition planning
Many practitioners combine composition estimates with dietary software. Fat mass and lean mass values help set protein targets, caloric deficits, and realistic time frames for safe progress toward body composition goals.
Monitoring health risk alongside composition
Elevated body fat mass, especially with high waist measurements, is associated with increased cardiometabolic risk. Results should always be interpreted alongside clinical markers, lifestyle factors, and guidance from qualified healthcare professionals.
Frequently asked questions
How accurate is this body fat mass calculator?
The equations used are research based and generally reliable for population averages. Individual results can differ from imaging methods. Treat values as approximate indicators instead of definitive medical measurements.
Which method should I choose for estimating body fat?
If you know reliable circumference measurements, the US Navy method is often informative. When you only know height and weight, the BMI based equation is convenient. Direct percentage should match laboratory or field tests.
Can I use this tool while gaining muscle mass?
Yes. Tracking lean mass estimates over time helps you see whether weight gain mainly comes from muscle or fat. Combine data with performance logs and training notes to interpret composition changes more effectively.
How often should I measure my body fat mass?
Many people recheck every two to four weeks. Measuring too frequently can be distracting because normal fluid shifts create noise. Pick consistent conditions, such as morning measurements, to improve comparison between different sessions.
Is this calculator suitable for athletes and beginners?
The equations can be used by both athletic and sedentary populations. However, extreme physiques, such as competitive bodybuilders or endurance elites, may experience larger estimation errors and should rely on specialist assessments when possible.
Can children or teenagers use this calculator safely?
These formulas were mainly developed for adults. For growing children and adolescents, body composition should be evaluated using age specific charts and paediatric guidance from healthcare professionals rather than generic adult equations.
Should I change my treatment without consulting a professional?
No. Estimates from this calculator are not a diagnosis or prescription. Never modify medications, clinical treatment plans, or rehabilitation programs based only on these values. Always discuss major decisions with qualified healthcare providers.