What this tool does and when to use it
This calculator estimates your body fat percentage from your height, neck and waist, plus hips for women, using the US Navy formula from 1984. It also shows your fat mass, lean mass and fitness category on the ACE chart. The Navy method is usually within 3 to 4 percentage points of a DEXA scan, so it is best used the same way each month to track the trend rather than as an exact number.
How to measure for the body fat calculator
Use a soft, non stretchy tape measure against bare skin. Stand up straight and relaxed, don't suck in, and keep the tape level and snug without pressing into the skin. Take each measurement three times and use the average.
- Neck: just below the larynx (Adam's apple), with the tape sloping slightly down to the front.
- Waist: men at the level of the navel, women at the narrowest point of the waist.
- Hips (women only): around the widest part of the buttocks.
- Height: without shoes.
The US Navy body fat formula
The US Navy developed this method in 1984 to estimate body fat quickly and cheaply for service members. It uses the difference between your waist and neck, and your hips for women, relative to your height. In studies it usually lands within 3 to 4 percentage points of more expensive methods such as underwater weighing or DEXA scans, which makes it a useful way to track change over time.
The formula, worked through
The formula uses base 10 logarithms and measurements in inches.
- Men: body fat % = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76
- Women: body fat % = 163.205 × log10(waist + hips − neck) − 97.684 × log10(height) − 78.387
Example, man: 5 ft 10 in (70 in) tall, neck 15 in, waist 34 in. Waist minus neck is 19, so 86.010 × log10(19) = 109.99. Then 70.041 × log10(70) = 129.23. 109.99 − 129.23 + 36.76 = 17.5%, in the fit range for men.
Example, woman: 5 ft 5 in (65 in) tall, neck 13 in, waist 30 in, hips 38 in. Waist plus hips minus neck is 55, so 163.205 × log10(55) = 284.04. Then 97.684 × log10(65) = 177.09. 284.04 − 177.09 − 78.387 = 28.6%, in the average range for women.
Body fat percentage by waist size
Your waist moves the result more than anything else. These rows come from the calculator above, for a 5 ft 10 in man with a 15 in neck and a 5 ft 5 in woman with a 13 in neck and 38 in hips. Every 2 inches off the waist takes about 3 to 5 points off the estimate for men and about 2.5 points for women.
| Man's waist | Body fat | Category |
|---|---|---|
| 30 in | 8.7% | Athletic |
| 32 in | 13.4% | Athletic |
| 34 in | 17.5% | Fit |
| 36 in | 21.3% | Average |
| 38 in | 24.6% | Average |
| 40 in | 27.8% | Above average |
| 42 in | 30.6% | Above average |
| Woman's waist | Body fat | Category |
|---|---|---|
| 26 in | 23.2% | Fit |
| 28 in | 25.9% | Average |
| 30 in | 28.6% | Average |
| 32 in | 31.1% | Average |
| 34 in | 33.5% | Above average |
| 36 in | 35.9% | Above average |
Your own result depends on your height, neck and hips too, so enter yours above for a personal estimate.
Body fat percentage chart
| Category | Women | Men |
|---|---|---|
| Essential fat | 10 to 13% | 2 to 5% |
| Athletic | 14 to 20% | 6 to 13% |
| Fit | 21 to 24% | 14 to 17% |
| Average | 25 to 31% | 18 to 24% |
| Above average | 32% and above | 25% and above |
Categories from the American Council on Exercise (ACE).
Using your result
Women naturally carry more essential fat than men, so healthy ranges differ. Very low body fat is not healthier, and can disrupt hormones and energy. To change your body composition, pair enough protein and strength training with the calorie target from the calorie calculator, and compare your result with the BMI calculator and the ideal weight calculator. If you plan to lose fat, the weight loss calculator turns a goal into a weekly plan and date.
Sources: Hodgdon JA, Beckett MB, Naval Health Research Center reports, 1984; American Council on Exercise body fat categories.
