Body Fat Percentage Calculator - Navy Method & BMI
Calculate your body fat percentage using the US Navy method and BMI method. Get your fitness category and healthy body fat range for your age and gender.
About this calculator
Body fat percentage says more about your health than weight or BMI, because it separates fat from muscle and bone. This calculator uses the US Navy tape-measure method, which needs only a tape, and compares it with a BMI-based estimate.
It returns your body fat percentage and a category such as essential, athletic, fit, average or obese, along with your fat mass, lean body mass and BMI. It is an estimate within a few percentage points, good for tracking change over time.
How to use it
- Choose Gender, Age, Height and Weight.
- Measure your Waist at the navel and your Neck below the Adam's apple. Women also measure the Hips at the fullest point.
- Press Calculate Body Fat.
- Read the percentage, the category and the fat and lean masses.
Navy method
The US Navy method estimates body fat from tape measurements. Men: BF% = 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450. Women: BF% = 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450, with all measurements in centimetres. Fat mass is body weight times BF%, and lean mass is the remainder.
Worked example
Man, 175 cm, 75 kg, waist 85 cm, neck 37 cm
| Body fat | 17.7% (Fit) |
| Fat mass | 13.3 kg |
| Lean body mass | 61.7 kg |
| BMI | 24.5 |
Measure in the morning, relaxed, and take each measurement twice. A 1 cm error at the waist changes the result by about a percentage point.
This tool gives general information, not medical advice. Talk to a doctor or dietitian before making changes to your diet, exercise or medication.
Tips and common mistakes
- Use the same tape, time of day and method each time. The trend matters more than a single value.
- Do not pull the tape tight. It should lie flat on the skin.
- The Navy method is less accurate for very muscular or very lean people.
- For a better reading, compare with skinfold calipers or a DEXA scan.
- Aim for a healthy range rather than a number: roughly 10 to 20% for men and 18 to 28% for women.
Frequently asked questions
What is a healthy body fat percentage?
Roughly 10 to 20% for men and 18 to 28% for women, depending on age.
How accurate is the Navy method?
Within about 3 to 4 percentage points for most people.
Is BMI the same as body fat?
No. BMI uses only height and weight and cannot tell muscle from fat.
How do I measure my waist?
At the navel, relaxed, after breathing out.
How often should I measure?
Every two to four weeks.
Why do women need a hip measurement?
Women store more fat at the hips, and the formula accounts for it.