Body Fat Calculator
Estimate your body fat percentage with the US Navy method
Your estimated body fat
ACE category bands
How to Use
- Select your sex — The female formula also requires a hip measurement, so a hip field appears when “Female” is selected.
- Choose your units — Toggle between metric (cm) and imperial (inches). The default follows the page language, and your entered values convert automatically when you switch.
- Enter your measurements — Height, neck, and waist (plus hip for the female formula), taken with a flexible tape measure.
- Read your result — Your estimated body fat percentage appears instantly, along with the ACE category band it falls into and the full band table for reference.
Features
- US Navy method — The Hodgdon-Beckett circumference formula used by the US military, requiring only a tape measure.
- Metric and imperial units — Locale-aware default (cm or inches) with one-click toggle and automatic value conversion.
- ACE category bands — Sex-specific bands (essential fat, athletes, fitness, average, obese) with your result highlighted.
- Input validation — Localized hints catch impossible entries, such as a waist smaller than the neck.
- 100% client-side privacy — All calculations run in your browser; your measurements never leave your device.
Use Cases
- Fitness tracking: Logging body fat trends week to week without buying a smart scale.
- Military preparation: Estimating compliance with service body-composition standards that use the same Navy tape method.
- Goal setting: Checking which ACE band you fall into before planning a cut or bulk.
- Quick screening: Getting a rough body-composition estimate when only a tape measure is available.
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- BMI Calculator — Body Mass Index, BMR, and daily calorie needs.
- Macro Calculator — Balance protein, carbs, and fat intake for your goals.
- Pace Calculator — Convert running pace, speed, and race finish times.
Frequently Asked Questions
How does the US Navy body fat method work?
The US Navy (Hodgdon-Beckett) method estimates body density from circumference measurements, then converts density to body fat percentage with the Siri equation. For men it uses height, neck, and waist; for women it also uses hip. You only need a tape measure — no scale or special device.
How accurate is the Navy method?
It is an estimate, not a measurement. Compared with lab methods like DEXA or hydrostatic weighing, the Navy formula can be off by roughly 3–4 percentage points in either direction. Accuracy drops for very lean athletes, elderly people, and body types the original study underrepresented. Use it to track trends over time rather than as a precise one-off number, and consult a health professional for a clinical assessment.
What do the ACE categories mean?
The American Council on Exercise classifies body fat into five bands. For men: essential fat 2–5%, athletes 6–13%, fitness 14–17%, average 18–24%, obese 25% and above. For women: essential 10–13%, athletes 14–20%, fitness 21–24%, average 25–31%, obese 32% and above. Dropping below the essential band is dangerous — very low body fat is not a health goal.
How should I take the measurements?
Measure on bare skin with a flexible tape, standing relaxed. Neck: just below the larynx, tape slightly sloping down at the front. Waist: at the navel for men, at the narrowest point for women. Hip (women only): at the widest point of the buttocks. Take each measurement twice and use the average.