The short answer
Body fat percentage is the share of your total weight that is fat. This calculator uses the US Navy circumference method: it estimates body fat from your height and neck and waist measurements, plus hips for women. It is a convenient estimate that can be off by several percentage points, not a medical scan.
Formulas and sources are named on this page. How we calculate.
How this is calculated
The US Navy method estimates body density from body circumferences and height, then converts it to a body fat percentage. It was published by Hodgdon and Beckett in 1984 for Navy body-composition screening. The tool converts inches to centimetres before using the formula below.
Men: body fat % = 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450
Women: body fat % = 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450
(all measurements in cm)
Worked examples
Man: height 180 cm, neck 38 cm, waist 85 cm.
- waist − neck = 85 − 38 = 47, and log₁₀(47) = 1.6721; log₁₀(180) = 2.2553
- Denominator = 1.0324 − 0.19077 × 1.6721 + 0.15456 × 2.2553 = 1.0620
- 495 ÷ 1.0620 = 466.1, and 466.1 − 450 = 16.1% body fat
Woman: height 165 cm, neck 32 cm, waist 75 cm, hips 98 cm.
- waist + hip − neck = 75 + 98 − 32 = 141, and log₁₀(141) = 2.1492; log₁₀(165) = 2.2175
- Denominator = 1.29579 − 0.35004 × 2.1492 + 0.22100 × 2.2175 = 1.0335
- 495 ÷ 1.0335 = 478.9, and 478.9 − 450 = 28.9% body fat
Categories. Results are labelled using the American Council on Exercise (ACE) chart, shown in the table below. We label the value as displayed to one decimal place.
How accurate is it?
Tape measurements are convenient but approximate. Small differences in where the tape sits, how tightly it is pulled, or hydration can move the result by a couple of percentage points, and the method as a whole can differ from the real figure by more. The CDC notes that DEXA scans measure body composition more precisely but are expensive and not widely available. Use this estimate to track change using the same method over time rather than as an exact number.
Who should not use it
The formula was developed for healthy adults. It is not suitable during pregnancy or for people under 18, and it can be unreliable for very muscular people, very lean people or those with medical conditions that change body shape.
Body fat categories
American Council on Exercise (ACE) body fat percentage chart| Category | Women | Men |
|---|
| Essential fat | 10 – 13% | 2 – 5% |
| Athletes | 14 – 20% | 6 – 13% |
| Fitness | 21 – 24% | 14 – 17% |
| Average | 25 – 31% | 18 – 24% |
| Higher than average (obese range) | 32% and above | 25% and above |
These are general reference ranges, not medical diagnoses. Essential fat is the lowest band on the chart and is not a goal to aim for.
Frequently asked questions
How accurate is the US Navy body fat method?
It is an estimate that can differ from the true figure by several percentage points. It is best used to follow your own trend with consistent measuring, rather than as an exact reading. DEXA and similar scans measure body composition more precisely.
What is a healthy body fat percentage?
The ACE chart treats 21 to 24% for women and 14 to 17% for men as the fitness range, and 25 to 31% and 18 to 24% as average. What is healthy for you depends on age, health and activity, so ask a doctor if you are unsure.
Why are the ranges higher for women?
The chart shows higher ranges for women at every level, for example 10 to 13% for essential fat compared with 2 to 5% for men. That is why the calculator asks for sex and, for women, hip measurements.
Where exactly should I measure?
Neck just below the Adam's apple. Waist at navel level for men and at the narrowest point for women. Hips at the widest point around the buttocks. Keep the tape level, snug and not compressing the skin.
How often should I measure body fat?
Because the estimate shifts with small measuring differences, many people compare readings taken every few weeks under the same conditions: same tape, same time of day and the average of two measurements.
Should I use body fat or BMI?
They answer different questions. BMI compares weight with height and cannot tell fat from muscle, while a body fat estimate tries to. Looking at both, with your waist size and a health professional's advice, gives a fuller picture. Try the BMI calculator too.
Disclaimer and editorial note
For information only, not medical advice. This calculator gives general estimates from the numbers you enter. It cannot diagnose, treat or prevent any condition and does not replace advice from a doctor, midwife, registered dietitian or other qualified professional who knows your history.
Written and maintained by the HealthFitnessHQ editorial team. We name the source of every formula and category used, and we review each calculator when guidance changes. Read how we work in our editorial policy and methodology.