Body Fat Calculator

About This Tool

This body fat percentage calculator estimates how much of your total weight is made up of fat tissue. It uses the U.S. Navy circumference method, which the military relies on because it needs nothing more than a tape measure and a few body measurements.

The tool supports metric and US units and, when you add your weight, also splits your body into fat mass and lean body mass. Because it is based on circumference measurements, the result is a screening estimate rather than a direct measurement of body composition.

How to Use the Body Fat Calculator

1. Select metric or US units.
2. Select your sex, as the male and female formulas differ.
3. Enter your height, neck, and waist measurements (plus hip for women).
4. Optionally add your weight to also estimate fat mass and lean mass.
5. Click Calculate.
6. Review the estimate, along with your fat mass and lean mass if a weight was entered.
7. Read the limitations before interpreting the result.

For more consistent tracking, use the same method and take your measurements under similar conditions each time.

Taking Body Measurements

This tool estimates body composition from body circumferences. It does not directly scan or measure fat tissue. Use a flexible measuring tape, keep it level, and do not pull it tightly into the skin. Repeat each measurement and use a consistent position.

Height

Stand upright without shoes and measure from the floor to the top of your head.

Neck

Measure just below the larynx. Keep the tape level and comfortably close to the skin.

Waist

Measure horizontally around the abdomen at the navel for men, and at the narrowest point for women.

Hips

Where required, measure around the widest part of the hips while keeping the tape parallel to the floor.

These steps show how to measure body fat percentage indirectly, through the measurements used by the formula.

What Is Body Fat Percentage?

Body fat percentage is the proportion of your total body weight made up of fat tissue. The remaining weight is described as lean body mass and includes muscle, bone, organs, water, and other non-fat tissue.

For example, a person weighing 80 kg with an estimate of 25% has approximately:

• 20 kg of fat mass
• 60 kg of lean body mass

Fat Mass and Lean Body Mass

When you enter your weight, the calculator uses your estimated body fat percentage to split it into two parts:

Body Fat Mass = Body Weight × Estimated Fat Percentage

Lean Body Mass = Body Weight − Body Fat Mass

U.S. Navy Circumference Method

The U.S. Navy method estimates body composition from your height and selected circumferences. For men it uses the waist and neck; for women it adds the hip measurement. It takes the logarithm of these differences, adjusts for height, and returns a body fat percentage.

Small differences in tape placement or tension can affect the answer, so the result should be treated as an estimate rather than a direct measurement. The method works best for average builds and is less accurate at the extremes of leanness or muscularity.

Body Fat Percentage vs BMI

Body fat percentage and BMI answer different questions. BMI compares your weight with your height, while a body fat estimate targets the proportion of your weight that is actually fat.

Neither result provides a complete medical assessment by itself.

Why Results Can Differ

Body fat tools can return different estimates because they use different inputs and assumptions. Your own result may also vary because of:

• Tape placement
• Measurement tension
• Hydration
• Time of day
• Muscle mass
• Body shape
• Rounding

When monitoring changes, focus on the trend produced by one consistent method rather than comparing unrelated tools.

Reference Categories

The reference ranges shown with your result can help place an estimate in context, but they should not be treated as diagnoses or universal targets. Age, sex, muscle mass, pregnancy, health history, and the method used can all affect interpretation.

Male and female bodies carry fat differently, so the calculator compares your result against sex-specific ranges. These ranges offer general context, but personal health decisions should not be based on a category alone.

Limitations of This Body Fat Calculator

This estimate has several limitations:

• It estimates rather than directly measures fat tissue.
• Measurement mistakes can change the output.
• It is less accurate for very lean or very muscular people.
• Reference categories do not diagnose a medical condition.
• Results may not be suitable during pregnancy or for children.
• One result should not guide major diet, exercise, or treatment decisions.

Professional methods such as DXA scans, hydrostatic weighing, air-displacement plethysmography, and assessments performed by qualified professionals may provide more detailed information.

Start Calculating

Enter your measurements above and use the body fat calculator to review an estimated percentage, plus your fat mass and lean mass when a weight is entered. Interpret the result as general information rather than a final health assessment.

Medical Disclaimer

This tool and its results are provided for general informational and educational purposes only. The figures are estimates based on the measurements you enter and should not be treated as a diagnosis, medical evaluation, or exact measurement of body composition. Results may not account for pregnancy, age-related changes, medical conditions, athletic muscle mass, hydration, or individual differences. Do not make major decisions about diet, exercise, medication, or treatment based solely on this result. Always consult a qualified doctor or healthcare professional for advice about your health and body composition.