Rex says
Same equations the textbooks use — just way less awkward. Pop in your stats and I'll tell you what the number actually means for you.
Try a scenario
Click to load — tweak from there.Inputs
Result
Body fat
17.4%
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One click, a permanent link with your numbers baked in.
How to use this
- 1Enter units.
- 2Enter sex.
- 3Enter height.
- 4Enter neck circumference.
- 5Enter waist circumference.
- 6Enter hip (women only).
- 7Read your body fat on the right — it updates as you type.
- 8Hit Share to keep the scenario or send it to someone.
About this calculator
Uses the U.S. Navy circumference method (neck, waist, hips for women) to estimate body fat percent.
Worked example
Using the values the calculator loads with:
Inputs
- Units: Imperial (lb, in)
- Sex: Male
- Height: 70
- Neck circumference: 15
- Waist circumference: 34
- Hip (women only): 38
Results
- Body fat: 17.4%
What each field means
Inputs
- Units
- Pick the option that matches your situation — the maths changes per option. Choices: Metric (kg, cm), Imperial (lb, in).
- Sex
- Pick the option that matches your situation — the maths changes per option. Choices: Male, Female.
- Height
- The height used in the calculation. Starts at 70 so you have a working example on load.
- Neck circumference
- The neck circumference used in the calculation. Starts at 15 so you have a working example on load.
- Waist circumference
- The waist circumference used in the calculation. Starts at 34 so you have a working example on load.
- Hip (women only)
- The hip (women only) used in the calculation. Starts at 38 so you have a working example on load.
Results
- Body fat
- Returned as a percentage and shown as the headline result. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How does the body fat percentage calculator work?
Uses the U.S. Navy circumference method (neck, waist, hips for women) to estimate body fat percent.
What do I need to enter?
6 values: units, sex, height, neck circumference, waist circumference, and hip (women only). Each field starts with a sensible default, so you can change one number at a time and watch the result move.
What does the body fat result mean?
It is returned as a percentage and updates live as you edit the inputs, so you can compare two or three versions of a scenario in a few seconds.
Is this calculator free, and do I need an account?
Yes, it's free, and no account is required. Nothing you type is stored on our servers — the maths runs entirely in your browser.
How accurate is the result?
It applies the standard formula exactly, so the arithmetic is precise. Population formulas describe averages; individual bodies vary, especially at the extremes of height, age, or muscle mass.
Who is this tool for?
It's built for anyone tracking a health or training target and wanting the standard formula applied correctly, without a signup or an app.
Accuracy and limitations
- Population formulas describe averages; individual bodies vary, especially at the extremes of height, age, or muscle mass.
- Results do not account for medical conditions, medication, or pregnancy.
- Use this as a directional reference, not a diagnosis — talk to a clinician before acting on it.
Related tools
Cite this calculator
Writing about this topic? Grab a citation — every link helps keep these tools free.
RevenueLab. (2026). Body Fat Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/body-fat
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/body-fat" target="_blank" rel="noopener">Body Fat Calculator — RevenueLab</a> (2026).</p>
Source: [Body Fat Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/body-fat) (2026).