Body Fat Calculator

Estimate your body fat percentage from tape measurements — the US Navy method.

Height cmNeck cmWaist cm

—estimated body fat

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About the Body Fat Calculator

This estimates your body fat percentage from a few tape-measure body measurements, using the US Navy method — no special equipment, scales or scans needed. Body fat percentage is a more useful indicator of body composition than weight or BMI alone, since it distinguishes fat from muscle. It's popular with people tracking fitness progress who want a rough number they can measure at home over time. It's the same style of tape-measure test the US military uses to estimate body fat — this tool uses the well-known US Navy formula — and it works for both men and women, needing only your height and a couple of measurements rather than a scale.

Tracking fitness more broadly? Also see the Ideal Weight Calculator or the BMR Calculator for daily calorie needs.

How it works — the formula

The US Navy body-fat formula uses your height and circumference measurements (in inches internally; metric entries are converted):

Men: 495 ÷ (1.0324 − 0.19077 × log₁₀(waist − neck) + 0.15456 × log₁₀(height)) − 450
Women: 495 ÷ (1.29579 − 0.35004 × log₁₀(waist + hip − neck) + 0.22100 × log₁₀(height)) − 450

Measure at the navel for waist, below the larynx for neck, and at the widest point for hip. The result is shown as a percentage with a rough fitness category.

Assumptions and behaviour

Measure snugly but without compressing the skin, ideally in the morning, and take each measurement a couple of times for consistency.
Women also measure the hip; men need only neck and waist.
Categories shown (athletic, fitness, average, etc.) are approximate, based on common fitness-industry ranges, and differ for men and women.
Metric measurements are converted to inches for the formula.

Limitations

The Navy method is an estimate, not a precise measurement. It's typically within a few percentage points of a DEXA or hydrostatic result but can be off more for very lean, very heavy, or unusually-proportioned bodies.
Accuracy depends entirely on measurement technique — a centimetre off on the waist noticeably changes the result, so measure carefully and consistently.
It uses the traditional two-category (male/female) formulas and assumes typical fat distribution.
This is general information, not medical advice; for a clinical body-composition assessment, see a professional.

Privacy

The calculation runs entirely in your browser. Your measurements are never uploaded or stored.

Frequently asked questions

Is this body fat calculator free?

Yes — free, no sign-up, no limits, runs in your browser.

What measurements do I need?

Height, neck and waist for men; women also measure the hip. Measure the waist at the navel, the neck below the larynx, and the hip at its widest point.

How accurate is the Navy method?

It's a reasonable estimate, usually within a few percentage points of a lab method like DEXA, but it depends heavily on measuring accurately and consistently.

Why is body fat better than BMI?

BMI can't tell fat from muscle, so a muscular person reads as 'overweight'. Body fat percentage measures composition directly, giving a clearer picture.

Is this the military body fat test (Army, Marine Corps, Air Force)?

It uses the US Navy circumference (tape-measure) formula — the same kind of tape test the US armed forces use to estimate body fat. The exact pass/fail cut-offs differ by branch, but the measurement method and body-fat equation here are the standard Navy calculation.

Can I estimate body fat from my BMI instead?

This uses tape measurements rather than BMI, which is more accurate because BMI can't separate fat from muscle. A BMI-based body-fat estimate exists if you only have height and weight, but measuring your neck, waist (and hip) here gives a better body-composition number.

Does it work for women as well as men?

Yes. It has separate formulas for men and women — men measure height, neck and waist; women also measure the hip — so it estimates body fat percentage for both.

How do I measure accurately?

Use a snug (not tight) tape, measure in the morning, keep the tape level, and take each measurement two or three times to average out errors.

Is this medical advice?

No. It's a general estimate. For a precise, clinical body-composition assessment, consult a health professional.

Is my data uploaded?

No. Everything runs locally in your browser; nothing is sent or stored.

Written by Lakshay Kumar(TechLakshay)

A QA Automation Engineer by trade, Lakshay's real passion is untangling complex problems into simple, working solutions — which is exactly why FreeMyTask exists. On Instagram, he channels that same instinct into helping 26,000+ content creators with SEO education, motivation, and hands-on query solving.

Last updated: September 5, 2026