Body Fat Calculator
Estimate your body fat percentage from your height and neck and waist measurements, plus hips for women, with the U.S. Navy circumference method, in centimetres or inches. Add your weight to see fat and lean mass.
Runs in your browser. Your data is not uploaded.How our tools work
Just below the larynx (Adam’s apple).
At the narrowest point.
At the widest point.
For fat and lean mass.
How do I estimate my body fat percentage?
The U.S. Navy method estimates body fat from tape measurements: height, neck and waist for men, plus hips for women. A man 178 cm tall with a 37 cm neck and an 85 cm waist comes out at about 17.2% body fat. It is an estimate, typically within a few percentage points of lab methods.
- Choose centimetres or inches and the version of the formula: male or female.
- Measure your height and your neck just below the larynx. Men measure the waist at the navel; women measure it at the narrowest point, and the hips at the widest point.
- Read your estimated body fat percentage. Add your weight to see fat mass and lean mass.
Formulas & Methods
Men (cm)
Example: waist 85, neck 37, height 178: 17.2%
Women (cm)
Example: waist 75, hip 100, neck 33, height 165: 29.4%
Fat and lean mass
Example: 80 kg at 17.2%: 13.8 kg fat, 66.2 kg lean
Key features
Just a tape measure
No scales or devices needed: three or four measurements and your height.
Centimetres or inches
Inches are converted exactly and use the same published equations.
Fat and lean mass
Add your weight to split it into fat mass and lean mass.
How accurate is it?
The equations were fitted by the U.S. Navy in the 1980s to predict body fat measured by underwater weighing. For most adults they land within a few percentage points of lab methods, but individual errors can be larger, especially for very muscular people, people with obesity, and older adults. Measuring technique matters too: a tape pulled tighter or placed differently changes the result.
Use the same tape, the same spots and the same time of day to compare results over time; the trend is more meaningful than one number. This is an estimate, not a medical measurement or a diagnosis.
Frequently Asked Questions
Why does the formula need my neck measurement?
Neck size tracks lean, muscular build, while the waist tracks fat stored around the middle. Subtracting the neck from the waist corrects for frame size and muscle.
Is this more accurate than BMI?
It measures something different. BMI compares weight with height and can’t tell muscle from fat; the tape method estimates the fat itself, so it often suits muscular people better. Both are screening estimates.
What is a healthy body fat percentage?
There is no single agreed range. One published approach (Gallagher and colleagues, 2000) links ranges to the healthy BMI cut-offs, and the results differ with sex, age and ethnic group. Women carry more essential fat than men, so their ranges sit higher. Compare your result only with a range for your sex and age, and ask a doctor or registered dietitian what it means for you.
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