Body Fat Calculator

Estimate your body-fat percentage from simple tape measurements using the US Navy method, with category.

100% Browser-Based • Local Processing
Units
cm
cm
cm
kg

Measure relaxed, with a soft tape, level with the floor: neck below the larynx, waist at the navel, hips at the widest point. The US Navy method is an estimate — calipers and DEXA are more accurate. Not medical advice.

Estimated body fat

19.8%

Category Average
Fat mass 15.8 kg
Lean mass 64.2 kg
Method and working

The method

%fat = 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450

Your numbers

waist − neck = 52.0 cm, height = 180.0 cm → 19.8% body fat.

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Privacy Focused

🔒 Local Processing. Your numbers never leave your device.

Instant Results

🌐 Fully Client-Side. Runs instantly in your browser.

No Signup

⚡ No accounts. No API keys. Just open and use.

Browser Based

🚀 No installs, no sign-ups, no server round-trip.

Overview

What is a Body Fat Calculator?

A Body Fat Calculator estimates your body-fat percentage from a few tape measurements. Using the US Navy method (height, neck, and waist — plus hip for women), it gives an estimated body-fat percentage and category. Unlike BMI, it reflects body composition, so it's a useful complement. It runs privately in your browser; results are an estimate.

Body-fat percentage tells you how much of your weight is fat versus everything else (muscle, bone, water) — often more meaningful than weight or BMI alone. The US Navy circumference method estimates it with just a tape measure.

This calculator applies that method and shows your category. It runs entirely in your browser, so your measurements stay private. Treat the result as an estimate, not a precise measurement.

Guide

How to estimate your body fat

Step 1: Choose your sex and units, and enter your height

Choose your sex and units, and enter your height.

Step 2: Measure and enter your neck and waist (and hip, for women) circumference

Measure and enter your neck and waist (and hip, for women) circumference.

Step 3: Read your estimated body-fat percentage and category

Read your estimated body-fat percentage and category.

Screens

Body Fat Calculator in action

Body Fat Calculator estimating body-fat percentage in the browser.
Body fat %
Body-fat percentage with category from tape measurements.
Category
Estimating body fat on a phone, no app installed.
Mobile (stacked)
Details

The tape-measure method — and its limits

The US Navy method estimates body fat from body circumferences, which correlate with fat distribution: for men it uses height, neck, and waist; for women it adds the hip measurement. It's popular because it needs only a tape measure and gives a reasonable estimate for most people. The big advantage over BMI is that BMI uses only height and weight and can't distinguish fat from muscle — a muscular person can have a 'high' BMI but low body fat — whereas a body-fat estimate targets composition directly, so the two together give a fuller picture. General body-fat categories differ by sex (women naturally carry more essential fat): rough ranges put 'fitness/athletic' lower and 'average' higher, with the calculator showing where your estimate falls. Be realistic about accuracy: the result is sensitive to how precisely you measure (pull the tape snug but not tight, at the right spots), and circumference formulas are estimates that can be off for individual body shapes. More accurate methods exist — skinfold calipers, bioelectrical impedance, and especially DEXA scans — if you need precision. It's a helpful trend-tracker and screening estimate, not a medical measurement, and it isn't medical advice. Everything computes locally. Compare with the BMI and Ideal Weight calculators.

Support

Frequently Asked Questions

How does the body fat calculator work?

It uses the US Navy circumference method, which estimates body-fat percentage from body measurements: height, neck, and waist for men, plus hip for women. These circumferences correlate with how much fat you carry, so the formula produces a reasonable estimate from just a tape measure.

How is this different from BMI?

BMI uses only height and weight and can't tell fat from muscle, so a muscular person may look 'overweight' by BMI despite low body fat. A body-fat estimate targets composition directly. Using both together gives a fuller picture than either alone — BMI for a quick weight screen, body fat for composition.

How accurate is the estimate?

It's a reasonable estimate but not precise — accuracy depends heavily on measuring correctly (snug tape, correct locations) and the formula can be off for unusual body shapes. For more accuracy, skinfold calipers, bioelectrical impedance scales, or a DEXA scan are better. Use this to track trends over time rather than as an exact figure.

What's a healthy body-fat percentage?

It varies by sex and age — women carry more essential fat than men. Very roughly, athletic ranges are lower and 'average' higher, with too-low and too-high both carrying health considerations. The calculator shows the category your estimate falls in, but healthy ranges are individual; treat them as general guidance.

How should I measure for the best result?

Use a flexible tape, measure on bare skin, and keep the tape snug but not compressing. Measure the neck below the larynx, the waist at the navel (men) or the narrowest point (women), and the hip at the widest point (women). Measure consistently each time so changes you track are real, not measurement noise.

Is the body fat result medical advice?

No. It's a screening estimate from a circumference formula, sensitive to measurement and individual variation, and it doesn't assess your health. Use it to understand your body composition and track changes, and consult a healthcare or fitness professional, or use a clinical method like DEXA, for anything important. It isn't medical advice.

Is it free, and do I need to sign up?

Yes, it's completely free with no account, no trial, and no limit on how many times you use it. It runs entirely in your browser, so there's no sign-in wall — just open the page and calculate.

Is my data private?

Yes. Everything is calculated in your browser — the numbers you enter are never sent to a server, and nothing is stored once you close the tab. That keeps any personal figures (salary, loan, health) on your own device.

Does it work on mobile?

Yes. It runs in your phone's browser with nothing to install, so you can calculate on Android or iOS. The layout adapts to small screens, so entering numbers and reading the result is easy on the go.

Does it work offline?

Once the page has loaded, the calculation runs entirely on your device, so it keeps working without a connection. You only need to be online to open the page the first time — which is also why nothing you enter is uploaded.

Can I copy or share the result?

Yes. You can copy the result to your clipboard with one click, and many results can be shared. Because everything is calculated locally, copying is instant with no upload step.

How accurate is it, and is this professional advice?

The math is accurate for the inputs you give, and the formula is shown so you can verify it. But results are estimates for general use, not professional advice — finance calculators use simplified assumptions and ignore fees and rate changes, and health calculators are general estimates, not medical advice. For important decisions, consult a qualified professional.

Still have questions?

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