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How do I estimate my body fat percentage from measurements?

Enter your height, neck and waist (plus hip for women) into AnyTool Body Fat Calculator in metric (cm) or imperial (in), and it estimates your body-fat percentage with the U.S. Navy circumference method. It shows your ACE category — essential fat, athletes, fitness, average or obese — on a colour-coded gauge, and if you add your weight and age it also splits your fat and lean mass and runs a second BMI-based (Deurenberg) estimate as a cross-check. Everything is calculated in your browser, so nothing is uploaded.

  • U.S. Navy method needs only height, neck and waist (plus hip for women)
  • Sex-specific ACE categories on a live colour-coded gauge
  • Add weight to split body fat mass and lean (fat-free) mass
  • Add age for a BMI-based (Deurenberg) cross-check estimate
  • 100% in your browser — no upload, no signup, works offline

What is

Body Fat Percentage

Body-fat percentage is the share of total body weight made up of fat, with the rest being lean (fat-free) mass such as muscle, bone, organs and water. The U.S. Navy circumference method estimates it from tape measurements (neck, waist, and hip for women) and height using the Hodgdon–Beckett equations, validated to roughly ±3–4 % against hydrostatic weighing. The American Council on Exercise (ACE) groups results into essential fat, athletes, fitness, average and obese ranges that differ for men and women.

Calculators

Related terms

U.S. Navy methodLean body massACE categoriesDeurenberg BMI estimate

Frequently Asked Questions

For men it is 495 ÷ (1.0324 − 0.19077·log10(waist − neck) + 0.15456·log10(height)) − 450, with all measurements in centimetres; women add hip and use different constants.

The U.S. Navy (Hodgdon–Beckett) circumference method estimates body fat from tape measurements. In metric, men use 495 ÷ (1.0324 − 0.19077·log10(waist − neck) + 0.15456·log10(height)) − 450, and women use 495 ÷ (1.29579 − 0.35004·log10(waist + hip − neck) + 0.22100·log10(height)) − 450, with every length in centimetres. AnyTool computes this live as you type and also accepts inches, converting for you.

Under the ACE categories, the fitness range is about 14–17 % for men and 21–24 % for women, with the athlete range a little lower.

The American Council on Exercise groups body fat into essential fat (2–5 % men, 10–13 % women), athletes (6–13 % men, 14–20 % women), fitness (14–17 % men, 21–24 % women), average (18–24 % men, 25–31 % women) and obese (25 %+ men, 32 %+ women). Women naturally carry more essential fat than men. AnyTool highlights exactly which band your estimate falls into.

The U.S. Navy circumference method is a field estimate accurate to roughly ±3–4 % versus hydrostatic weighing — useful for tracking trends, not a clinical measurement.

Circumference methods estimate body fat from body shape, so they are good for tracking change over time but less precise than DEXA, hydrostatic weighing or a Bod Pod. They can overstate body fat in very muscular people and understate it in slim people with little muscle, and are not validated during pregnancy. Measure with a flexible tape at the same landmarks each time and watch the trend rather than a single number.

No. Every calculation runs in your browser, so nothing is sent to a server and it works offline.

AnyTool Body Fat Calculator computes every result locally in JavaScript using a unit-tested engine. Your height, weight and tape measurements are never uploaded, there is no tracking, and the page keeps working offline after the first load.

Detailed Explanation

Methodology

How the Body Fat Calculator Works

AnyTool Body Fat Calculator estimates body-fat percentage in the browser using the U.S. Navy (Hodgdon–Beckett, 1984) circumference method as its primary engine. In metric, men use 495 ÷ (1.0324 − 0.19077·log10(waist − neck) + 0.15456·log10(height)) − 450 and women use 495 ÷ (1.29579 − 0.35004·log10(waist + hip − neck) + 0.22100·log10(height)) − 450, with every length in centimetres; imperial inches are converted automatically. The result is classified into sex-specific American Council on Exercise (ACE) categories, plotted on a colour-coded gauge, and — when weight is supplied — split into fat mass and lean (fat-free) mass. All arithmetic is pure client-side JavaScript shared through a unit-tested engine.

  • Primary engine is the U.S. Navy circumference method (Hodgdon–Beckett)
  • Men use neck + waist; women add hip; height in cm or inches
  • Classified live against sex-specific ACE categories with no Calculate button
  • Weight splits the result into fat mass and lean body mass
  • All math is client-side JavaScript — no server round-trip
How It Works

Navy Circumference Method and BMI Cross-Check

The Navy circumference method reads body shape from tape measurements, so it captures fat distribution that BMI alone cannot. As a secondary cross-check the calculator also computes the Deurenberg (1991) BMI-based estimate, %BF = 1.20·BMI + 0.23·age − 10.8·sex − 5.4 (sex: male = 1, female = 0), whenever weight and age are entered. The two estimates are shown side by side: close agreement suggests consistent measurements, while a gap greater than about 3 % is expected because the BMI method cannot see body shape. The ACE categories used for classification — essential fat, athletes, fitness, average and obese — differ between men and women to reflect the higher essential fat women carry.

  • Navy method captures body shape; BMI method does not
  • Deurenberg estimate: 1.20·BMI + 0.23·age − 10.8·sex − 5.4
  • Two estimates shown side by side as a sanity check
  • ACE categories differ for men and women
  • Essential fat is higher for women (10–13 %) than men (2–5 %)
Limitations

Circumference Methods Are Field Estimates

The U.S. Navy circumference method is validated to roughly ±3–4 % against hydrostatic weighing, which makes it useful for tracking change over time but less precise than laboratory methods such as DEXA, hydrostatic weighing or air-displacement plethysmography (Bod Pod). Because it infers body fat from girth, it can overstate body fat in very muscular people and understate it in slim people with little muscle, and it is not validated during pregnancy. AnyTool states these limits plainly and recommends measuring with a flexible tape at consistent landmarks and watching the trend rather than any single reading.

  • Accurate to about ±3–4 % versus hydrostatic weighing
  • Less precise than DEXA, hydrostatic weighing or Bod Pod
  • Can overstate fat in the very muscular, understate in the very lean
  • Not validated during pregnancy
  • Best used to track trends with consistent measurements
Privacy & Security

Privacy and Offline Use

Because all computation runs in the browser, your height, weight and tape measurements are never sent to a server, there is no account or tracking, and the page works offline after first load. The calculator is built on a shared, unit-tested body-fat engine so its behaviour is consistent and verifiable.

Body-fat estimation: in-browser (AnyTool) vs typical online calculators
CapabilityAnyToolTypical online calculators
ProcessingRuns in your browserOften server-side
Primary methodU.S. Navy circumference (Hodgdon–Beckett)Usually U.S. Navy
Cross-checkBMI-based (Deurenberg) estimate tooOften a single method
UnitsMetric and imperial, liveUsually one at a time
CategoriesSex-specific ACE bands on a gaugeOften a single label
Mass splitFat mass and lean body massFrequently omitted
Works offlineYes (PWA)No
Cost / signupFree, no signupOften ad-heavy or gated

AnyTool computes every estimate locally and uploads nothing.