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
16.5%
Category
Fitness
Fat mass (lb)
30.6
Lean mass (lb)
154.4
Pounds to lose for a lean target
13.4
BMI for reference
26.5
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One click, a permanent link with your numbers baked in.
How to use this
- 1Enter sex.
- 2Enter height (in).
- 3Enter weight (lb).
- 4Enter neck (in).
- 5Enter waist (in).
- 6Enter hip (women) (in).
- 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
The US Navy circumference method estimates body fat from neck, waist, and (for women) hip measurements. It is within a few points of DEXA for most people and free.
Worked example
Using the values the calculator loads with:
Inputs
- Sex: Male
- Height: 70 in
- Weight: 185 lb
- Neck: 15.5 in
- Waist: 34 in
- Hip (women): 38 in
Results
- Body fat: 16.5%
- Category: Fitness
- Fat mass (lb): 30.6
- Lean mass (lb): 154.4
- Pounds to lose for a lean target: 13.4
- BMI for reference: 26.5
What each field means
Inputs
- Sex
- Pick the option that matches your situation — the maths changes per option. Choices: Male, Female.
- Height (in)
- The height used in the calculation, measured in in. Starts at 70 in so you have a working example on load. Accepted range: 48–84 in.
- Weight (lb)
- The weight used in the calculation, measured in lb. Starts at 185 lb so you have a working example on load. Accepted range: 60–500 lb.
- Neck (in)
- The neck used in the calculation, measured in in. Starts at 15.5 in so you have a working example on load. Accepted range: 8–30 in.
- Waist (in)
- The waist used in the calculation, measured in in. Starts at 34 in so you have a working example on load. Accepted range: 18–80 in.
- Hip (women) (in)
- The hip (women) used in the calculation, measured in in. Starts at 38 in so you have a working example on load. Accepted range: 20–80 in.
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.
- Category
- Returned as a plain value. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Fat mass (lb)
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Lean mass (lb)
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- Pounds to lose for a lean target
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
- BMI for reference
- Returned as a decimal number. It recalculates instantly whenever you change an input, so you can compare scenarios without reloading.
FAQ
How does the navy method body fat calculator work?
The US Navy circumference method estimates body fat from neck, waist, and (for women) hip measurements. It is within a few points of DEXA for most people and free. The underlying maths is: Men: 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76.
What do I need to enter?
6 values: sex, height, weight, neck, waist, and hip (women). 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). Navy Body Fat Calculator. Retrieved from https://www.revenuelab.fyi/toolbox/body-fat-navy
<p>Source: <a href="https://www.revenuelab.fyi/toolbox/body-fat-navy" target="_blank" rel="noopener">Navy Body Fat Calculator — RevenueLab</a> (2026).</p>
Source: [Navy Body Fat Calculator — RevenueLab](https://www.revenuelab.fyi/toolbox/body-fat-navy) (2026).