Body Fat Calculator
Estimate your body fat percentage with the U.S. Navy tape-measurement method.
Body Fat Calculator — your inputs
- Sex
- Male
- Age
- 30 yrs
- Height
- 180 cm
- Weight
- 80 kg
- Neck
- 38 cm
- Waist
- 84 cm
- Unit system
- Metric
Key takeaways
- This uses the U.S. Navy circumference method — a tape measure and a formula, validated against hydrostatic weighing to about ±3–4 percentage points.1
- Essential fat is roughly 2–5% for men and 10–13% for women. Below that is not lean, it is dangerous.2
- Women carry more essential fat than men for reproductive reasons, which is why the healthy ranges differ by about ten points and always will.
- Measurement technique causes more error than the formula does. Measure at the same time of day, on bare skin, with the tape snug but not compressing.
- It answers the question BMI cannot: how much of your weight is fat rather than muscle.
How to use this calculator
Select your sex — women also enter hip circumference.
Enter your height, weight, neck, and waist measurements.
Keep the tape level and snug, not compressing the skin, for the most accurate result.
Understanding your result
Your body fat percentage is the fraction of your weight that is fat mass. The U.S. Navy method estimates it from circumference measurements using published regressions.
ACE categories (Essential, Athletes, Fitness, Average, Obese) differ for men and women and are shown in the table below.
How the tape method works
The U.S. Navy method exploits a simple regularity: fat is not distributed randomly. It accumulates preferentially around the waist in men and around the waist and hips in women, while the neck stays comparatively lean. The ratio between those circumferences, scaled by height, predicts total body fat well enough to be useful — which is why the U.S. military has used it since 1984 to screen hundreds of thousands of people who are never going near a DEXA scanner.1
It is a prediction, not a measurement. Validated against hydrostatic weighing it lands within about three to four percentage points for most people. That is precise enough to tell an athletic body from an unhealthy one, and not precise enough to argue about a single point.
Where it goes wrong
The method assumes a typical fat distribution. Very muscular people with thick necks are read as leaner than they are; people who store fat mainly on the hips and thighs rather than the waist are read as leaner too. If your body does not follow the average pattern, neither will the answer.
Body fat categories
| Category | Men | Women |
|---|---|---|
| Essential fat (danger) | 2–5% | 10–13% |
| Athletes (success) | 6–13% | 14–20% |
| Fitness (success) | 14–17% | 21–24% |
| Average (warning) | 18–24% | 25–31% |
| Obese (danger) | 25% and above | 32% and above |
- Essential (2–6)
- Athletic (6–14)
- Fitness (14–18)
- Average (18–25)
- Obese (25–40)
| Category | Range |
|---|---|
| Essential | 2 to 6 % |
| Athletic | 6 to 14 % |
| Fitness | 14 to 18 % |
| Average | 18 to 25 % |
| Obese | 25 to 40 % |
Lower is not better
Essential fat is called that because the body cannot function without it — it is structural, hormonal and neurological, not storage. Sustained very low body fat in women is associated with menstrual disruption and bone loss, which the ACSM describes as part of the female athlete triad.4 Chasing a single-digit number is a health decision, not a fitness one.
Measuring properly
Technique introduces more error than the formula. Three tape measurements taken carelessly can move the result by five percentage points, which is larger than the method's own margin.
- Neck. Just below the larynx, tape sloping slightly downward at the front. Do not flex.
- Waist. Men measure at the navel; women at the narrowest point. Measure at the end of a normal exhale — not sucked in, not pushed out.
- Hips (women). The widest point of the buttocks, tape level all the way round.
- Every time. Bare skin, same time of day, tape snug enough to sit flat but not to compress the tissue. Take each measurement twice and use the average.
Morning, before eating, after using the bathroom, is the most repeatable moment. Consistency matters more than getting any single reading exactly right: what you are actually watching is the direction of travel over months.
Reading the number alongside other measures
Body fat percentage answers how much. It does not answer where, and where turns out to matter independently — abdominal fat carries more cardiometabolic risk than the same mass on the hips, which is why the WHO treats waist circumference as a risk marker in its own right.5
- Pair it with [waist-to-hip ratio](/calculators/waist-hip-ratio-calculator) for the distribution question.
- Pair it with [BMI](/calculators/bmi-calculator) to see whether a high BMI is muscle or fat — the single most useful thing this calculator does.
- Use [lean body mass](/calculators/lean-body-mass-calculator) to track what you are keeping during a deficit. Losing weight while lean mass holds steady is the goal; losing both is not.
Terms used on this page
- Essential fat
- Fat the body requires to function — in cell membranes, nerve tissue, bone marrow and organs. Distinct from storage fat, and not something to minimise.
- Hydrostatic weighing
- Underwater weighing, long the reference standard for body composition. Accurate but impractical, which is why circumference formulas exist at all.
- Lean body mass
- Total weight minus fat mass: muscle, bone, organs and water. What you are trying to preserve when losing weight.
The formula
- Man, height 180 cm, neck 38 cm, waist 84 cm
- waist − neck = 46
- BF% = 495 / (1.0324 − 0.19077×log10(46) + 0.15456×log10(180)) − 450
Source: U.S. Navy method. Published clinical/scientific formula.
Limitations
- Circumference-based estimates are less accurate than DEXA or hydrostatic weighing.
- Accuracy depends on careful, consistent tape placement — measure at the same anatomical points each time.
- The BMI-based estimate is a rougher fallback and should not replace the tape method.
References
- 1.Development and evaluation of general body composition equations for U.S. Navy personnel. Hodgdon & Beckett, Naval Health Research Center Report 84-11, 1984.
- 2.American Council on Exercise body fat percentage categories. American Council on Exercise, 2024.
- 3.Healthy percentage body fat ranges: an approach for developing guidelines based on body mass index. Gallagher et al., American Journal of Clinical Nutrition 72(3):694–701, 2000.
- 4.Position stand: The female athlete triad. American College of Sports Medicine, Medicine & Science in Sports & Exercise 39(10), 2007.
- 5.Waist circumference and waist-hip ratio: report of a WHO expert consultation. World Health Organization, 2011.
Frequently asked questions
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Open calculatorRelated articles
BMI vs. Body Fat Percentage: Which Actually Matters?
BMI is everywhere, but it can't tell muscle from fat. Here's what each measure captures, where each one misleads, and how to read them together.
Read articleHow to Measure Body Fat at Home (Without Calipers)
A practical guide to the U.S. Navy tape method — where to place the tape, how to avoid the common errors, and how it compares to scales and scans.
Read articleWaist-to-Hip Ratio vs. BMI: Which Predicts Health Risk Better?
Where you store fat matters as much as how much you carry. What waist-to-hip ratio measures, what the WHO thresholds mean, and when it beats BMI.
Read articleNot medical advice. This calculator is for general informational purposes only and is not a substitute for professional medical guidance. Always consult a qualified healthcare provider before making decisions about your health. Read the full medical disclaimer.
Printed from mystatura.com — for general information only, not medical advice.