How accurate is the Navy method?

Studies put the standard error at roughly 3–4 percentage points against DEXA. It is far more informative than BMI but not a laboratory measurement.

What is a healthy body-fat percentage?

Commonly cited fitness ranges are about 14–17% for men and 21–24% for women, with essential fat around 3–5% and 10–13% respectively.

Why did my number jump overnight?

Waist measurements move with digestion, hydration and salt intake. Measure at the same time of day and compare weekly averages.

Body Fat Calculator

The US Navy circumference method estimates body-fat percentage from a few tape measurements. It needs no special equipment and tracks changes well over time, which makes it more useful than BMI for judging body composition.

Fill in the fields above and select Calculate to see your result and the full working.

Please note: Health calculators on this site provide general estimates based on population-level formulas. They are not medical advice and cannot account for your individual medical history. Speak to a qualified healthcare professional before making decisions about diet, medication or training.

Formula used

Males: %BF = 495 ÷ (1.0324 − 0.19077·log₁₀(waist − neck) + 0.15456·log₁₀(height)) − 450. Females use waist + hip − neck with different constants.

How to use this calculator

Measure with a flexible tape held snug but not compressing the skin, ideally first thing in the morning.
Men need height, neck and waist; women also need hip circumference.
Keep the same measuring points every time so changes are comparable.
Calculate to see the estimated percentage and its fitness band.

Example calculation

A man 175 cm tall with a 38 cm neck and 85 cm waist:

waist − neck = 47 cm

495 ÷ (1.0324 − 0.19077 × log₁₀(47) + 0.15456 × log₁₀(175)) − 450

≈ 18.6% body fat — the 'average' band.

What does this result mean?

Circumference methods typically fall within about 3–4 percentage points of a DEXA scan, and they are most useful for tracking direction rather than pinning down an exact figure. A falling percentage with stable weight means you are losing fat and holding muscle — usually the goal. Very low body fat carries its own risks, particularly for hormonal health.

Frequently asked questions

How accurate is the Navy method?: Studies put the standard error at roughly 3–4 percentage points against DEXA. It is far more informative than BMI but not a laboratory measurement.
What is a healthy body-fat percentage?: Commonly cited fitness ranges are about 14–17% for men and 21–24% for women, with essential fat around 3–5% and 10–13% respectively.
Why did my number jump overnight?: Waist measurements move with digestion, hydration and salt intake. Measure at the same time of day and compare weekly averages.

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