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Body Fat Percentage Calculator

Estimate your body fat percentage from tape measurements using the US Navy method, with lean mass and healthy ranges by sex.

Body Fat Calculator

The equation and the healthy ranges differ.

Measure below the larynx, tape sloping slightly down at the front.

At the navel, relaxed, at the end of a normal breath out.

Body fat

18.5%

Average for a man · 14.8 kg of fat
Lean82%
  • Lean mass65.2 kg82%
  • Fat mass14.8 kg18%
Body composition

Lean mass

65.2 kg

Muscle, bone, organs, water

Fat mass

14.8 kg

Category

Average

To reach healthy

1.4 kg

Target 78.6 kg

Ranges for men

  • Essential fat0–5%
  • Athletic6–13%
  • Fitness14–17%
  • Average18–24%
  • Above average25%+

Ranges from the American Council on Exercise. Women carry more essential fat than men — roughly 10–13% against 2–5% — so the two scales are genuinely different, not offset versions of each other.

How this was worked out

  • MethodUS Navy circumference
  • Waist − neck50.0 cm
  • Height180.0 cm
  • Body fat18.5%

Accurate to roughly ±3 percentage points against a DEXA scan, and least reliable at the extremes because it infers composition from shape rather than measuring it. Measure at the same time of day with the tape snug but not compressing, and track the trend rather than any single reading.

The link carries the values you entered, so whoever opens it sees the same result. Nothing is stored on our side — the numbers travel in the link itself.

How the body fat calculation works

Body fat percentage measures what your weight is made of. That is a different question from the one BMI answers, and the reason to have both.

Why not just use BMI?

BMI is weight divided by height squared. It knows nothing about composition, so a muscular athlete and a sedentary person of the same height and weight get an identical BMI despite completely different bodies. A large proportion of professional rugby players and NFL linemen are classified obese by BMI.

Body fat percentage measures the thing that actually matters. BMI remains useful as a population screening tool — it is cheap and correlates well across large groups — but for an individual it is the weaker measure.

The US Navy method

This calculator uses the circumference equations the US Navy adopted in the 1980s:

  • Men: 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76
  • Women: 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387

with measurements in inches — metric input is converted before the equation is applied.

It needs a tape measure and nothing else, which is why it is the method people can actually use repeatedly. Accuracy is roughly ±3 percentage points against a DEXA scan, and it degrades at the extremes because it infers composition from shape rather than measuring it.

The women's equation requires a hip measurement; the men's does not, because male fat distribution is more strongly predicted by the waist alone.

Measuring properly

Technique matters more than the equation. Small errors compound because the calculation works on the difference between measurements:

  • Neck — just below the larynx, tape sloping slightly down at the front.
  • Waist — men at the navel; women at the narrowest point. Relaxed, at the end of a normal breath out. Do not pull it in.
  • Hips — widest point, feet together.

Use a flexible tape, snug but not compressing. Measure at the same time of day, ideally before eating. Take each measurement three times and average.

Healthy ranges

From the American Council on Exercise:

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%+ 32%+

Women require substantially more essential fat than men — it supports hormonal and reproductive function. Applying the male scale to a woman makes a perfectly healthy figure look like a problem, which is why the two columns exist.

Use it as a trend

Any single reading carries measurement error. The value of this method is that it is cheap enough to repeat, so measure every two to four weeks under the same conditions and watch the direction. A trend across three measurements tells you far more than any one of them.

For clinical precision, DEXA is the practical gold standard. Bioelectrical impedance scales are convenient but heavily affected by hydration, and can swing several points between morning and evening on the same body.

Disclaimer: This calculator provides estimates for general information only and is not medical advice. It cannot account for your medical history, body composition, or individual needs. Talk to a doctor or registered dietitian before making changes to your diet or exercise.

Frequently asked questions

What is a healthy body fat percentage?

For men, roughly 14% to 24% covers the fitness and average bands; for women, 21% to 31%. Women require substantially more essential fat than men - around 10% to 13% against 2% to 5% - because it supports hormonal and reproductive function. Applying the male scale to a woman makes a healthy figure look like a problem, which is why the ranges differ.

How accurate is the Navy body fat method?

Within about 3 percentage points of a DEXA scan for most people, which is good enough to track progress and not good enough to treat as exact. It infers composition from body shape, so it is least reliable at the extremes and for people whose fat distribution is unusual. Measure consistently and follow the trend rather than fixating on any single reading.

Why is body fat percentage better than BMI?

BMI is weight divided by height squared and knows nothing about what the weight is made of. A muscular athlete and a sedentary person of the same height and weight get the same BMI despite completely different bodies - which is why many professional athletes are classified obese by it. Body fat percentage measures composition directly, which is the thing that actually matters for an individual.

How should I measure my waist and neck?

Neck just below the larynx, with the tape sloping slightly down at the front. Waist at the navel for men, or the narrowest point for women, relaxed and at the end of a normal breath out - do not pull it in. Hips at the widest point with feet together. Use a flexible tape, snug but not compressing, and average three readings taken at the same time of day.

Can I lose fat without losing weight?

Yes, and it is common early in a training programme. Gaining muscle while losing fat keeps the scale still while body composition improves substantially - which is precisely why tracking body fat percentage alongside weight is more informative than weight alone. It happens most readily in people new to resistance training or returning after a break.

Do body fat scales work?

Bioelectrical impedance scales are convenient but heavily affected by hydration, food, and even skin temperature - readings can swing several percentage points between morning and evening on the same body. They are reasonable for spotting a trend if you always measure under identical conditions. For a single accurate number, DEXA is the practical gold standard.

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