Body Fat % Calculator
Estimate your body-fat percentage using the US Navy method from waist, neck and height measurements.
Written by Rahman · Last reviewed
Quick answer
The US Navy method estimates body fat from circumference measurements (waist and neck for men, plus hip for women), set against height. It typically lands within about 3 to 4 percentage points of laboratory reference methods, which is accurate enough to follow a trend over time but not enough to treat any single reading as precise.
American Council on Exercise ranges. Essential fat is the minimum needed for normal physiological function — below it is not a target.
Uses the US Navy body-fat formula. Measure neck just below the larynx, waist at navel level, and (for women) hip at the widest point. Circumference methods carry an error of roughly 3–4 percentage points against a DEXA scan, and they read least accurately at the extremes.
Results are general screening estimates, not medical advice or a diagnosis. They can read inaccurately for athletes, older adults, children and during pregnancy. Speak to a doctor or registered dietitian before changing your diet, exercise or medication.
About the Body Fat % Calculator
Body-fat percentage is a more meaningful health indicator than BMI alone because it distinguishes muscle from fat. Two people with identical BMI can have very different body compositions and very different health risks.
This calculator uses the US Navy body-fat formula, which estimates body-fat percentage from simple measurements: height, neck and waist for men, plus hip circumference for women. Compared with skin-fold calipers or DEXA scans it is less precise but requires no special equipment.
Men: BF% = 495 / (1.0324 − 0.19077·log(waist−neck) + 0.15456·log(height)) − 450 Women: BF% = 495 / (1.29579 − 0.35004·log(waist+hip−neck) + 0.22100·log(height)) − 450
All measurements in centimetres. Measure neck just below the larynx, waist at navel level, and hip at the widest point.
How accurate the circumference method is
The US Navy method was developed to be repeatable in the field with nothing but a tape measure. That is its strength and the source of its limits.
- It typically lands within about 3 to 4 percentage points of hydrostatic weighing or DEXA, which are the reference methods.
- It infers fat from where you carry girth, so it reads high for people who carry weight abdominally and low for those who do not, at the same true body-fat percentage.
- Measurement technique dominates the error. A centimetre of difference in where the tape sits at the waist moves the result more than most real week-to-week change.
- It has not been validated for pregnancy, for children, or for people with substantially altered body proportions.
Because the method is consistent even where it is not precise, it tracks change well. Measure at the same time of day under the same conditions and read the trend across several weeks rather than any single figure.
Frequently Asked Questions
How accurate is the US Navy method?
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It typically lands within about 3 to 4 percentage points of more precise methods like DEXA scans, which is good enough for tracking changes over time. Use the same person doing the measuring for consistency.
What is a healthy body-fat percentage?
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Using the American Council on Exercise ranges shown above: for men, 6–13% is the athlete range, 14–17% is fitness, 18–24% is average, and 25%+ is classed obese (below 6% is essential fat, the minimum needed for normal function, not a target to go under). For women, 14–20% is athlete, 21–24% is fitness, 25–31% is average, and 32%+ is obese (below 14% is essential fat).
Why does the formula differ for men and women?
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Women naturally carry more essential body fat than men (about 12% essential vs 3% for men) and store it differently, partly in the hips. The formula reflects this by including hip circumference.
How can I lower body fat?
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Body composition responds to overall calorie balance and resistance training, but the right approach (including whether and how much of a calorie deficit is appropriate) depends on individual health factors. Speak with a doctor or registered dietitian for personalized guidance rather than a generic target; the [Calorie Calculator](calc:calorie-calculator) shows your estimated maintenance calories as a descriptive starting point for that conversation.
Sources
- Gallagher et al. (2000), American Journal of Clinical Nutrition — Healthy percentage body fat ranges — Peer-reviewed basis for reading body fat as banded ranges rather than a single target, deriving healthy percentage ranges from BMI, age and sex. It is not the source of the ACE athlete/fitness/average bands shown above; those are ACE's own, and ACE no longer publishes them at a URL that resolves, so they are named in prose rather than linked.