Body Fat Calculator
Body fat percentage, US Navy method.
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Body fat percentage tells you far more about your physique than the scales alone. Using nothing more than a tape measure, this calculator applies the US Navy method to estimate your body fat — and, if you add your weight, your fat and lean mass.
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Body Fat — The Quick Answer
The US Navy method estimates body fat from circumference measurements: height, neck, and waist (plus hip for women). It's a practical alternative to calipers or DEXA scans.
Shortcut
Men: 495 ÷ (1.0324 − 0.19077·log₁₀(waist − neck) + 0.15456·log₁₀(height)) − 450
Body fat categories (ACE / US Navy reference)
| Category | Men | Women |
|---|---|---|
| Essential | 2–5% | 10–13% |
| Athletic | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Above average | 25%+ | 32%+ |
Essential fat is the minimum the body needs for normal function — it's stored in organs, bone marrow, and the nervous system. Dropping below it isn't healthy.
How It Works
The Formulas
US Navy circumference method
Formula
Men: BF% = 495 / (1.0324 − 0.19077·log₁₀(waist − neck) + 0.15456·log₁₀(height)) − 450 Women: BF% = 495 / (1.29579 − 0.35004·log₁₀(waist + hip − neck) + 0.22100·log₁₀(height)) − 450
Variables
Body height
Measured without shoes, in centimetres or inches.
Circumferences
Neck at its narrowest just below the larynx; waist at the navel (men) or narrowest point (women).
Hip circumference
Measured at the widest point, needed for the women's formula.
Note: All measurements use the same units. The method correlates well with more precise techniques but is a population-level estimate — individual results can differ.
Worked Example: Body Fat for a 180 cm Man
US Navy method, measurements in centimetres (waist 85, neck 38)
Take the measurements
Waist 85 cm, neck 38 cm, height 180 cm
Subtract neck from waist
85 − 38 = 47 cm
Apply the Navy formula (men)
495 ÷ (1.0324 − 0.19077·log₁₀47 + 0.15456·log₁₀180) − 450
Compute the result
495 ÷ 1.062 − 450 ≈ 16.1% body fat
Read the category
≈16% falls in the 'Fitness' range for men
Reference Guide
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletic | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Above average | 25% and above | 32% and above |
What Your Body Fat Result Means
Reading the estimate — and how far to trust it
Essential fat (about 2–5% for men, 10–13% for women) is the minimum the body needs for normal function — protecting organs and supporting hormones. Dropping below it is not healthy and is rarely sustainable. Women biologically carry more essential fat than men.
Best for: Understanding why extremely low body fat is a warning sign
These ranges (roughly 6–17% for men, 14–24% for women) reflect a lean, active build. They're common targets for people who train regularly, but 'better' isn't always lower — chasing very low body fat can harm performance, recovery, and health.
Best for: A realistic, healthy target for most active adults
Higher body fat is linked to greater health risk at a population level, especially when combined with a large waist. If you want to reduce it, a modest calorie deficit plus resistance training preserves muscle while losing fat. This estimate is a prompt to look closer, not a diagnosis.
Best for: Pairing with waist-to-hip ratio and a professional assessment
The US Navy method typically lands within about 3–4% of a DEXA scan — good for tracking change over time, but not a precise clinical reading. Careful, consistent measurement matters more than the single number. This is a general wellness estimate, not medical advice.
Best for: Tracking your own trend with identical measuring each time
What Is Body Fat Percentage?
Body fat percentage is the share of your total body weight that is fat, as opposed to muscle, bone, water, and organs. It tells you far more about body composition than weight or BMI alone, because two people at the same weight can carry very different amounts of fat and muscle. This tool uses the US Navy circumference method, which estimates body fat from a few tape measurements — height, neck, and waist for men, plus hips for women. It's free, private, and repeatable at home, which makes it well suited to tracking change over time, even though lab methods like DEXA are more precise.
Key Features
💡 Pro Tips
- →Measure first thing in the morning, before eating or drinking, for the most consistent readings — and always measure the same way each time if you're tracking change.
- →Keep the tape snug but not compressing the skin, and measure the waist at the navel for men and the narrowest point for women; the neck just below the larynx.
- →Take each measurement two or three times and average them — a single reading can be off by a centimetre, which shifts the result.
- →Track the trend over weeks rather than fixating on one figure; body fat changes slowly, so day-to-day noise is larger than real change.
Common Mistakes
Measuring at the wrong spot
The formula is sensitive to where you place the tape. Measuring the waist too high or low, or pulling the tape tight, can shift the result by several percent. Use the standard landmarks and a consistent, gentle tension.
Treating the estimate as a precise clinical reading
The Navy method is an estimate, typically within 3–4% of a DEXA scan. It's excellent for tracking your own trend but shouldn't be read as an exact medical figure.
Mixing units
Entering some measurements in centimetres and others in inches gives a nonsense result. Pick one unit and use it for every measurement.
Chasing the lowest possible number
Below the essential-fat range, health and performance suffer. For most people a lean, sustainable range beats an extreme one, and very low body fat carries real risks.
Research & Citations
Sources and standards referenced for the factual claims on this page
- [1]
Hodgdon, J. A. & Beckett, M. B. (1984). Prediction of percent body fat for U.S. Navy men and women from body circumferences and height. Naval Health Research Center, Reports 84-11 & 84-29.
Origin of the US Navy circumference formulas used by this calculator.
View source - [2]
American Council on Exercise (ACE) (2023). Percent Body Fat Norms for Men and Women. ACEfitness.org.
Body fat percentage categories (essential, athletic, fitness, average).
View source - [3]
Jackson, A. S. & Pollock, M. L. (1985). Practical assessment of body composition. The Physician and Sportsmedicine, 13(5).
Context on circumference and skinfold body-composition estimation.
View source
This calculator is a reference tool, not a substitute for professional advice. Verify important health, financial, legal, or safety decisions with a suitably qualified professional.
Last updated: October 7, 2026
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Frequently Asked Questions
What is a healthy body fat percentage?
For men, roughly 14–17% is a typical 'fitness' range and 18–24% average; for women, about 21–24% fitness and 25–31% average. Women naturally carry more essential fat than men. The right target depends on your goals and health.
How accurate is the Navy body fat method?
It's reasonably accurate — typically within about 3–4% of a DEXA scan for most people — and far better than relying on BMI alone. Accuracy depends on careful measurements, since even a centimetre of error shifts the result.
Where do I measure my waist and neck?
For men, measure the waist at the navel; for women, at the narrowest point of the torso. Measure the neck just below the larynx, angling the tape slightly downward at the front. Keep the tape snug but not compressing the skin.
Why does the calculator need different measurements for men and women?
Body fat distribution differs by sex, so the Navy formulas use different inputs. Men use neck and waist; women need waist and hip as well, because their fat distributes differently around the hips and thighs.