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Body Fat Calculator

U.S. Navy method body fat percentage from circumferences.

Improving fitnessStep 1 of 6

Best for: Use it to track fat loss over time (trend matters more than the absolute number).

Complete guide
See benchmark ranges Why this result happened View assumptions
Country (units):

Input

How it's calculated & sources

Method: U.S. Navy circumference (tape) method using log-base-10 of body measurements. Source: Hodgdon & Beckett, Naval Health Research Center. Reviewed June 2026. Circumference estimates carry a few-percent margin vs DEXA.

Key assumptions
  • US Navy tape method
  • Estimate, about +/-3-4%

Educational estimate only — not medical advice. Consult a qualified healthcare professional for decisions about your health.

Free & no sign-up · runs entirely in your browser. Results are estimates for general information, not professional advice — verify important decisions with a qualified expert. Last reviewed June 2026.

How it works

U.S. Navy method:

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 (cm)

Example

Male, 175 cm, 85 cm waist, 38 cm neck ≈ 17% body fat.

Frequently asked questions

How accurate is the Navy method?+

±3–4% vs DEXA. Good enough to track progress over time.

Continue your journey

Where people usually head next.

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BMR Calculator
Basal metabolic rate using the Mifflin-St Jeor formula.
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TDEE Calculator
Total Daily Energy Expenditure for any activity level.
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Calorie Calculator
Daily calories to lose, maintain or gain weight.
🥗
Macro Calculator
Daily carbs, protein and fat for any goal and split.

Complete guide

Quick answers

Short, sourced answers to the questions people (and AI assistants) ask most.

What is Body Fat?
A body-fat calculator estimates the percentage of your body weight that is fat \u2014 a better health and fitness marker than weight or BMI alone.
Why does Body Fat matter?
It estimates body fat and flags health risk from belly fat.
How is Body Fat calculated?
The U.S. Navy method uses tape measurements (waist, neck, and hips for women) plus height in a validated formula; no special equipment needed. Formula: U.S. Navy tape method (log-based, uses waist, neck, height \u2014 and hips for women).
What is a good body fat?
Men ~10-20%, Women ~18-28% (fit)
What are common body fat mistakes?
Measuring inconsistently \u2014 same spot, same time of day.
When should you use the Body Fat Calculator?
Use it to track fat loss over time (trend matters more than the absolute number).

What is the Body Fat Calculator?

A body-fat calculator estimates the percentage of your body weight that is fat \u2014 a better health and fitness marker than weight or BMI alone.

How the Body Fat Calculator works

The U.S. Navy method uses tape measurements (waist, neck, and hips for women) plus height in a validated formula; no special equipment needed.

U.S. Navy tape method (log-based, uses waist, neck, height \u2014 and hips for women)
  • waist / neck / hips — Tape measurements in cm
  • height — In cm
  1. Enter your waist circumference — the distance around your waist, measured with a tape.
  2. Enter your neck circumference — the distance around your neck, used in the US Navy body-fat method.
  3. Enter your height — your height, entered in centimeters/meters or feet and inches.
  4. Enter your weight — your body weight, entered in kilograms or pounds.
  5. Enter your body fat percentage — the share of your body weight that is fat.
  6. Read the result, then change any input to compare scenarios instantly — the Body Fat Calculator recalculates as you type.

Understanding the inputs

What each value means, why it matters, and a typical range — so you can fill in the calculator with confidence.

Waist Circumference

The distance around your waist, measured with a tape.

Why it matters:
It estimates body fat and flags health risk from belly fat.
Typical range:
Health risk rises above about 94 cm (men) and 80 cm (women).
How it affects results:
  • Higher: Generally higher estimated body fat and risk.
  • Lower: Generally lower estimated body fat and risk.

Common mistake: Measuring at the wrong spot or pulling the tape too tight.

Neck Circumference

The distance around your neck, used in the US Navy body-fat method.

Why it matters:
It is subtracted from the waist measurement to estimate body fat.
Typical range:
Measured just below the larynx.
How it affects results:
  • Higher: Lowers the estimated body-fat percentage.
  • Lower: Raises the estimated body-fat percentage.

Common mistake: Measuring over a collar or flexing the neck, skewing the result.

Height

Your height, entered in centimeters/meters or feet and inches.

Why it matters:
It is paired with weight to judge healthy ranges and body composition.
Typical range:
Varies by person.
How it affects results:
  • Higher: A given weight reads as a lower BMI.
  • Lower: A given weight reads as a higher BMI.

Common mistake: Entering centimeters where meters are expected, or mixing units.

Weight

Your body weight, entered in kilograms or pounds.

Why it matters:
It feeds BMI, calorie, body-fat and dosing calculations.
Typical range:
Varies by person; tools accept metric or imperial.
How it affects results:
  • Higher: Raises BMI and calorie needs.
  • Lower: Lowers BMI and calorie needs.

Common mistake: Mixing units - entering pounds where kilograms are expected.

Body Fat Percentage

The share of your body weight that is fat.

Why it matters:
It reflects fitness and health better than weight or BMI alone.
Typical range:
Roughly 10% to 20% for fit men, 18% to 28% for fit women.
How it affects results:
  • Higher: More fat mass.
  • Lower: Leaner composition (very low can be unhealthy).

Common mistake: Trusting a single tape reading over the trend across weeks.

Benchmark reference

What counts as poor, average or excellent for this metric.

Body Fat

PoorVery high
Below averageAbove average
AverageAverage
Above averageFitness
ExcellentAthletic

Source: ACE / ACSM general ranges · Updated June 2026

Typical values

Body Fat:
Men ~10-20%, Women ~18-28% (fit)

Common interpretation errors

  • Tape estimates are approximate (about +/-3-4%)
  • Healthy ranges differ by sex and age
  • Track the trend, not one reading

What impacts results most

  1. 1.
    Waist (High impact)The main driver of the tape estimate.
  2. 2.
    Neck (Medium impact)Subtracted from the waist measurement.
  3. 3.
    Height (Medium impact)Scales the estimate.

Key assumptions

  • US Navy tape method
  • Estimate, about +/-3-4%

Body-fat categories (ACE)

EssentialMen 2\u20135% \u00b7 Women 10\u201313%
AthletesMen 6\u201313% \u00b7 Women 14\u201320%
FitnessMen 14\u201317% \u00b7 Women 21\u201324%
AverageMen 18\u201324% \u00b7 Women 25\u201331%
ObeseMen 25%+ \u00b7 Women 32%+

Worked example

Inputs: Male, height 178 cm, neck 38 cm, waist 85 cm (U.S. Navy method) Calculation: 495 ÷ (1.0324 − 0.19077·log10(waist−neck) + 0.15456·log10(height)) − 450 Result: 16.4% body fat What it means: Tape estimates carry ±3–4%; track the trend over weeks, not one reading.

Common mistakes to avoid

  • Measuring inconsistently \u2014 same spot, same time of day.
  • Trusting one reading; watch the trend.

Compared to alternatives

BMI vs Body Fat %

BMI is a quick height-weight screen; body-fat % measures actual composition.

BMIBody Fat %
MeasuresWeight relative to heightShare of weight that is fat
Best forFast population screeningTracking fat loss / fitness
WeaknessMisreads muscular peopleTape estimates vary ±3-4%

Bottom line: Use BMI for a quick check; use body fat % when muscle could distort BMI.

BMI calculator·Body Fat % calculator

Lean Mass vs Body Fat

Two sides of body composition.

Lean MassBody Fat %
MeasuresFat-free weightShare that is fat
Rises whenYou build muscleYou gain fat
Use forTracking muscleTracking fat loss

Bottom line: Watch both — holding lean mass while fat drops is the real recomposition goal.

Lean Mass calculator·Body Fat % calculator

Related concepts

How Body Fat connects to the concepts around it.

BMI:
Weight relative to height, a quick health screen.
Lean Body Mass:
Body weight excluding fat.
BMR:
The calories your body burns at complete rest.
Body Composition:
The body's make-up of fat versus lean mass.
Waist-Hip Ratio:
Waist divided by hip, a fat-distribution risk marker.
Ideal Weight:
A healthy target weight for your height.

Health learning path

A sensible order to learn these concepts.

BMIBody FatBMRTDEECalories

Reviewed sources & methodology

Methodology: Professional Estimate · Last reviewed June 2026.

Keywords: body, fat, navy.

This tool is for general information only and is not medical advice. Consult a qualified healthcare professional for decisions about your health.

Reviewed by the Free Tools Galaxy editorial team · Updated June 2026 · Calculated privately in your browser.

Frequently asked questions

Is the Body Fat Calculator free to use?+

Yes. Every tool on Free Tools Galaxy is 100% free, runs in your browser and requires no signup.

How accurate is the Body Fat Calculator?+

Body Fat Calculator uses the standard body fat formula in double-precision arithmetic, so the same inputs always produce the same result and you can verify any figure by hand. It is an educational estimate — real-world outcomes depend on your actual rates, rules and assumptions.

Do you store my inputs?+

No. The Body Fat Calculator runs entirely in your browser. Nothing is uploaded or saved to a server.

Can I use the Body Fat Calculator on mobile?+

Yes — the interface is fully responsive and works on phones, tablets and desktops.

What are common mistakes to avoid?+

The most frequent mistake is mixing units. Double-check your inputs use a single, consistent unit before clicking Calculate.

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U.S. Navy circumference body fat method (cm).

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