Body Fat Calculator
The Body Fat Calculator estimates your body fat percentage using the US Navy circumference method.
Body Fat Calculator
What the result means
Body fat percentage is the proportion of your body weight that is fat. The US Navy method uses circumference measurements for estimation.
How to use this calculator
- 1Select your sex.
- 2Enter your weight, height, waist and neck measurements.
- 3Women also enter hip measurement.
- 4Press Calculate.
The formula
The calculation uses a standard, verifiable formula. Here it is in its simplest form.
What each variable means
| Symbol | Name | Description |
|---|---|---|
| W | Weight | Body weight in kg. |
| H | Height | Height in cm. |
| Waist | Waist | Waist circumference in cm. |
| Neck | Neck | Neck circumference in cm. |
Step-by-step example
Example: Male, 70kg, 175cm, waist 80cm, neck 38cm
- 1Apply US Navy formula
- 2Body fat ≈ 15.2%
Result
≈ 15.2% body fat
What changes the result
- Measurement accuracy is critical.
- The method is an estimate, not a scan.
Edge cases to be aware of
Unusual situations handled correctly
- Very muscular individuals may be underestimated.
- The formula is less accurate for extreme body types.
Common mistakes
Avoid these errors
- Measuring at the wrong location.
- Using inches instead of cm.
Assumptions
- Measurements are taken correctly.
- Average body composition.
Limitations
- This is an estimate, not a DEXA scan.
- Not a medical diagnosis.
Key terms to know
Body fat percentage+
Essential fat+
Storage fat+
Lean mass+
US Navy method+
DEXA scan+
Real-world scenarios
Circumference measurement error
A waist measurement taken too loose or too tight changes the body-fat estimate.
What it means: Because the US Navy formula depends heavily on circumference, small measurement differences can shift the result by several percentage points. Use a tape measure flat against the skin at the narrowest waist point.
Muscular and lean individuals
A trained athlete and a sedentary person with the same height, weight, and circumference.
What it means: The formula can underestimate body fat in very muscular people because it relies on measurements rather than directly measuring body composition. It is a useful reference, not a lab result.
Age and body composition
Body fat tends to increase with age even when weight is stable.
What it means: The calculator does not include age. A younger and older adult with the same measurements may have different actual body-fat levels, which is a known limitation of the formula.
Fat mass and lean mass
A person weighing 80 kg with an estimated body-fat percentage of 20%.
What it means: Their fat mass is about 16 kg and lean mass about 64 kg. Understanding this split is often more useful than a single percentage, since lean mass drives metabolism and strength.
Related concepts
Body Mass Index
BMI relates weight to height but does not direct measured body fat. Comparing BMI and estimated body fat gives a fuller picture.
Metabolic rate and lean mass
Lean mass burns more calories at rest than fat. A body-fat estimate helps put BMR in context — more lean mass generally means a higher resting burn.
Calorie needs
Body composition influences how many calories you need. A body-fat estimate can help explain differences between otherwise similar people.
Ideal weight range
Ideal-weight formulas use height as their input. Combining them with body-fat estimates gives a more realistic picture than weight alone.