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Body Fat Percentage Calculator

Estimates body fat percentage from tape measurements using the US Navy method, with fat mass and lean mass in kilograms.

Calculators Nothing uploaded No sign-up Free, unlimited
Calculators tool
Women only
Enter your figures and press Calculate.
In short Body Fat Percentage Calculator is a free online tool on inputtesthub.com that estimates body fat percentage from tape measurements using the US Navy method, with fat mass and lean mass in kilograms. It needs no account, no download and no payment, and there is no daily usage limit. Everything is processed inside your own browser, so the data you paste is never uploaded to a server.

How to use the Body Fat Percentage Calculator

  1. Enter your figures in the input fields.
  2. The result updates as you type, together with the full working.
  3. Check the breakdown table to see exactly how the number was reached.

About the Body Fat Percentage Calculator

The Body Fat Percentage Calculator estimates body fat percentage from tape measurements using the US Navy method, with fat mass and lean mass in kilograms. It runs as plain JavaScript inside the page, which means there is no upload step, no queue and no size limit imposed by a server — the only limit is your own device.

What people use it for

  • A better body composition estimate than BMI when you have a tape measure.
  • Tracking recomposition when scale weight stays flat.
  • Setting a realistic target range.

The maths behind it

This tool uses the US Navy circumference method, which uses logarithms of neck, waist (and hip for women) measurements relative to height. Every intermediate value is shown on screen, so the result can be checked by hand.

Tape methods carry an error of roughly 3-4 percentage points against a DEXA scan, and measurement technique matters a lot. Measure the same way each time and watch the trend rather than a single number.

Frequently asked questions

Is there a limit on how often I can use the Body Fat Percentage Calculator?
Free, unlimited, and no email address required. You can use it a hundred times a day and nothing changes.
Is my data uploaded anywhere?
No. The Body Fat Percentage Calculator runs entirely in your browser using JavaScript. Nothing is transmitted, logged or stored, which you can verify yourself in the Network tab of your browser's developer tools.
How is the result calculated?
It uses the US Navy circumference method, which uses logarithms of neck, waist (and hip for women) measurements relative to height. The full working is printed under the result, so you can follow every step rather than trusting a black box.
Who is the Body Fat Percentage Calculator for?
The jobs it is built for: a better body composition estimate than BMI when you have a tape measure. Tracking recomposition when scale weight stays flat. Setting a realistic target range. It is built for exactly those cases rather than being a general-purpose tool with this bolted on.
Any caveats I should know about?
Tape methods carry an error of roughly 3-4 percentage points against a DEXA scan, and measurement technique matters a lot. Measure the same way each time and watch the trend rather than a single number.
Is the number rounded?
The calculation runs in double precision and the result is shown to ten significant figures, so converting a value and converting it back returns the original. What is displayed is rounded for readability; what is copied is not.

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