BodyCal

📏 Body Fat Calculator

Estimate your body fat percentage with the U.S. Navy method, see your fitness category, and get your fat mass and lean mass breakdown.

Your measurements

Gender
cm
kg
cm
cm
cm

Body fat

27.7%

Category

Average

Fat mass

17.2 kg

Lean mass

44.8 kg

Where you fall on the body fat scale

27.7%
EssentialAthletesFitnessAverageObese

Your body fat is in the average range for the general population. It's acceptable, but moving toward the fitness range through resistance training and a modest calorie deficit can improve health markers.

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What this body fat calculator does

This calculator estimates your body fat percentage — the share of your total body weight that is fat — using the U.S. Navy circumference method. Unlike a bathroom scale or BMI, it tells you something about your body composition: how much of you is fat versus lean tissue like muscle, bone, and organs. It then breaks your weight down into fat mass and lean mass, and shows where you sit on the standard fitness scale for your gender.

All you need is a tape measure. There are no calipers, no expensive scales, and nothing is sent to a server — every calculation happens in your browser.

How the Navy method works

The formula, developed by the Naval Health Research Center, uses the relationship between your height and the circumference of your neck, waist, and (for women) hips:

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

Measurements are taken in inches in the original equation; this tool accepts both metric and imperial and converts for you. The method works because fat distributes around the waist and hips in predictable proportions relative to frame size, so those circumferences are a surprisingly good proxy for overall fatness.

How to measure accurately

  • Neck:just below the larynx (Adam's apple), tape sloping slightly downward to the front. Don't flex.
  • Waist:men measure at the navel; women at the narrowest point. Stand relaxed and breathe out normally — don't suck in.
  • Hips (women): around the widest part of the buttocks.
  • Keep the tape snug but not compressing the skin, and take each measurement a few times, using the average for the most stable result.

Understanding your category

Body fat norms differ by sex because women carry more essential fat for hormonal and reproductive health. As a rough guide, the fitness range is about 14–17% for men and 21–24% for women, while the average range runs to roughly 24% and 31% respectively. Athletes typically sit below those bands. Both very low and very high body fat carry health risks, so leaner is not automatically better.

Body fat vs BMI — use both

BMI is quick but blind to composition: it can flag a muscular person as overweight and miss excess fat in someone with low muscle mass. Body fat percentage measures the thing that actually matters for metabolic health. The two are complementary — check your BMI for a population-level screen, this calculator for composition, and your ideal weight for a target range.

How to lower body fat (without losing muscle)

Reducing body fat comes down to a sustained, moderate calorie deficit paired with resistance training and enough protein (roughly 1.6–2.2 g per kg of body weight) to protect lean mass. Crash diets strip away muscle alongside fat and tank your metabolism. Use our calorie deficit calculator to set a safe daily target, then re-measure your body fat every few weeks — the tape measure will show progress the scale alone can hide.

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Frequently asked questions

How does the U.S. Navy body fat calculator work?

It uses the circumference method developed by the Naval Health Research Center. You measure your height, neck, and waist (plus hips for women), and a validated equation estimates your body fat percentage from the ratio of those measurements. It needs only a tape measure — no calipers or scales.

How accurate is the Navy method?

For most people it lands within about 3–4% of a clinical DEXA scan, which is impressive for a tape-measure method. Accuracy is best for people of average build and can drift for very lean or very muscular individuals. Treat it as a reliable way to track change over time rather than an exact clinical figure.

How should I measure my waist, neck, and hips?

Measure relaxed, without pulling the tape tight. Waist: at the narrowest point for women, at the navel for men. Neck: just below the larynx, with the tape sloping slightly down to the front. Hips (women): at the widest point of the buttocks. Take each measurement two or three times and use the average.

What is a healthy body fat percentage?

For men, roughly 14–24% is considered fitness-to-average and healthy, with athletes often at 6–13%. For women, roughly 21–31% is fitness-to-average, with athletes at 14–20%. Women naturally carry more essential fat than men. Below the essential threshold (about 3% for men, 12% for women) is unsafe.

What's the difference between body fat and BMI?

BMI only compares your weight to your height and can't distinguish muscle from fat — a muscular athlete can register as 'overweight' by BMI. Body fat percentage measures composition directly, so it's a better indicator of fitness. Using both together gives the clearest picture.

What are fat mass and lean mass?

Fat mass is the total weight of fat in your body; lean mass is everything else — muscle, bone, organs, and water. When you diet, the goal is to lose fat mass while preserving lean mass, which is why resistance training and adequate protein matter so much during weight loss.

Sources & scientific references

  1. Hodgdon JA, Beckett MB. Prediction of percent body fat for U.S. Navy men and women from body circumferences and height. Naval Health Research Center, 1984.
  2. American Council on Exercise (ACE) — Percent Body Fat Norms for Men and Women.
  3. Gallagher D, et al. Healthy percentage body fat ranges: an approach for developing guidelines based on body mass index. Am J Clin Nutr. 2000;72(3):694-701.

Medical disclaimer: Results are estimates and should not replace professional medical advice. Always consult a qualified healthcare provider before making changes to your diet, hydration, or exercise routine.

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