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Calculation Machine

Body Fat Calculator

US Navy method body fat from tape measurements.

Reviewed by the Calculation Machine team · How we check our maths

Your values

ⓘ Live results

Results
Body fat
18%
Category
Fitness
Fat mass
30.5 lb
Lean mass
139.5 lb

Quick answer

The US Navy method estimates body fat from the log of neck, waist and hip circumferences relative to height, accurate to about ±3%.

Worked example

Worked example

Using the values the calculator loads with.

Inputs

  • SexMale
  • Height69 in
  • Neck circumference15 in
  • Waist at navel34 in
  • Hip (women only)38 in
  • Weight170 lb

Result

  • Body fat18%
  • CategoryFitness
  • Fat mass30.5 lb
  • Lean mass139.5 lb

How to use the Body Fat Calculator

  1. 1Measure neck, waist and (for women) hips with a tape.
  2. 2Enter height and weight.
  3. 3Read the estimated body fat percentage.

Frequently asked questions

How accurate is the tape method?

Within about 3% of a DEXA scan for most people, and consistent enough to track change over time.

Where do I measure the waist?

At the navel for men, at the narrowest point for women, with the tape snug but not compressing skin.

About this calculator

What a body fat estimate can and cannot tell you

Body fat percentage is a better fitness marker than body weight because two people of the same weight can carry very different amounts of fat and muscle. This calculator estimates it from tape measurements, which is free and repeatable at home but less precise than a DEXA scan.

Treat the result as a trend line. Measured the same way, at the same time of day, a 1–2% change over several weeks is meaningful; a 0.5% swing between two days is mostly measurement noise.

How to measure so results are comparable

  • Measure in the morning before eating, with the tape snug but not compressing the skin.
  • Take each measurement twice and use the average.
  • Keep the tape level — a waist tape that dips at the back can add 2–3 cm.
  • Compare yourself with yourself. Method-to-method differences (tape, scales, calipers) are larger than most month-to-month changes.

Sources

More questions

What is a healthy body fat percentage?

Commonly quoted healthy ranges are about 10–20% for men and 18–28% for women, with athletes lower. Ranges shift with age.

Are smart scales accurate for body fat?

Bioimpedance scales are affected by hydration and can be off by several percent. They are fine for trends if used under the same conditions.

Why is my result different from my gym's scan?

Each method makes different assumptions. Pick one method and track it consistently.