What are the healthy body-fat ranges?

For men — Essential: 2–5%, Athletes: 6–13%, Fitness: 14–17%, Average: 18–24%, Obese: 25%+. For women — Essential: 10–13%, Athletes: 14–20%, Fitness: 21–24%, Average: 25–31%, Obese: 32%+. Women naturally carry more essential fat (for hormonal and reproductive health), which is why their healthy ranges are higher.

Why is my BMI 'normal' but body fat high?

This is known colloquially as 'skinny-fat' — a combination of low weight with low muscle mass and relatively high body fat percentage. BMI cannot detect it because it only sees total weight. The solution is strength training combined with adequate protein (1.6–2.2 g/kg body weight) to build muscle and improve body composition without necessarily changing weight.

Should I use calipers instead of this calculator?

Skinfold calipers, when used by a trained practitioner taking multiple sites, can be slightly more accurate but require practice and consistent technique. The tape-measure method needs only a soft tape measure and is extremely consistent over time if you measure at the same points and same posture each session. For tracking your own progress at home, the tape method is excellent.

How often should I measure my body fat?

Every 2–4 weeks to track real trends. Daily measurements fluctuate too much due to water retention, food volume, and minor measurement error. Monthly comparisons against the previous month give a cleaner signal of genuine body-composition change. Take photos in the same pose and lighting to complement the numbers.

Is very low body fat healthy?

No. Below essential fat levels (2–5% for men, 10–13% for women), hormone production suffers, immunity weakens, menstruation may cease in women, and injury recovery slows. Competitive bodybuilders hit extremely low percentages for stage but quickly return to healthier levels afterward — sustained very low body fat is not compatible with long-term health.

Can I use this calculator if I am very muscular?

Yes, but interpret the result cautiously. Highly muscular people may have thicker necks, which can inflate the body-fat estimate slightly. DEXA scans are a better choice for advanced athletes, powerlifters, and bodybuilders where a precise body-fat number matters for competition or program design.

Does body fat percentage change day to day?

Slightly — mainly due to water retention shifts. Real body fat changes are measured over weeks and months. If your body fat reading jumps by 2–3% in a day, it almost certainly reflects measurement variation or water weight, not actual fat gain or loss. Average several measurements across a week for the most honest reading.

Body Fat Calculator

Health

Estimate your body fat percentage using the US Navy measurement method.

Health

Body Fat Calculator

Generated on April 24, 2026

Height

Neck

Waist

?What is the Body Fat Calculator?

This body-fat calculator uses the US Navy tape-measure method to estimate body-fat percentage from your height, neck, and waist (plus hip for women). Originally developed in 1984 by Hodgdon and Beckett for the US military's fitness standards, it is a no-cost alternative to expensive DEXA scans or skinfold calipers. With careful measurement under good conditions, accuracy is within roughly ±3% of laboratory methods — more than adequate for tracking trends over time, setting realistic fitness goals, and monitoring body-composition progress during a diet or training cycle.

The Formula

Men: BFP = 495 / (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450. Women: similar with waist + hip − neck. All measurements in centimeters.

The US Navy formula derives body density from specific body-circumference measurements (waist − neck for men; waist + hip − neck for women) using logarithmic functions. Density is then converted into fat percentage via the Siri equation (495/density − 450), which is a standard body-composition conversion. All inputs must be in centimeters for the formula to work correctly; the calculator handles conversion automatically if you enter inches.

Practical Examples

A man at 180 cm with neck 40 cm and waist 85 cm has approximately 15% body fat — the 'Fitness' category for men.

A woman at 165 cm with neck 32 cm, waist 75 cm, and hip 95 cm has about 24% body fat — 'Fitness' for women.

A man at 175 cm with neck 42 cm and waist 100 cm has around 25% body fat — borderline high, 'Average' category.

A male athlete at 185 cm with neck 41 cm and waist 80 cm measures about 10% body fat — the 'Athlete' category.

A woman at 170 cm with neck 33 cm, waist 85 cm, and hip 100 cm has roughly 29% body fat — 'Average' category.

A man at 170 cm with neck 38 cm and waist 78 cm measures around 13% body fat — firmly within the 'Athlete' range, typical of lean recreational athletes.

Frequently Asked Questions

Generally within ±3% when compared to DEXA scans — the research gold standard. Accuracy depends heavily on careful, consistent measurement: take the waist at its narrowest point (usually just above the navel), hip at the widest point around the buttocks, and neck just below the Adam's apple. Measure at the same time of day in the same posture for the most reliable trends.

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Body Fat Calculator

Body Fat Calculator

?What is the Body Fat Calculator?

The Formula

Practical Examples

Frequently Asked Questions

How accurate is the US Navy method?

What are the healthy body-fat ranges?

Why is my BMI 'normal' but body fat high?

Should I use calipers instead of this calculator?

How often should I measure my body fat?

Is very low body fat healthy?

Can I use this calculator if I am very muscular?

Does body fat percentage change day to day?

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