Quick answer
The U.S. Navy body fat method estimates body fat percentage from height and neck and waist circumference (plus hip circumference for women) using logarithmic equations by Hodgdon and Beckett. Enter your tape measurements to get an estimate that is typically within about 3 to 4 percentage points.
It needs only a tape measure, which is why it is popular, but it is an estimate: it is not a clinical body composition test, and different sites use slightly different coefficients, so results can differ by a small amount between calculators.
Related tools: BMI Calculator: Find your Body Mass Index (BMI) and weight status.
How to use the Body Fat Calculator (U.S. Navy)
- Choose sex: Male and Female.
- Enter height (cm) (between 100 and 250).
- Enter neck (cm) (above 0).
- Enter waist (at navel) (cm) (above 0).
- Optionally, enter hip (widest point) (cm) (above 0).
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Sex | Choose one: Male; Female | Starts at Male |
| Height | A number, in cm | ≥ 100, ≤ 250 |
| Neck | A number, in cm | > 0 |
| Waist (at navel) | A number, in cm | > 0 |
| Hip (widest point) (optional) | A number, in cm. Required for women | > 0 |
Formula and method
Formula
Men: %BF = 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)
IEEE-754 double precision; shown to 1 decimal place unless stated.
Hodgdon–Beckett circumference equations used by the U.S. Navy. Accuracy is roughly ±3–4 percentage points. Informational estimate, not medical advice. Talk to a qualified health professional about your own situation.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Sex = Male; Height = 180; Neck = 38; Waist (at navel) = 85.
| Result | Value |
|---|---|
| Estimated body fat | 16.1% |
Example 2
Inputs: Sex = Female; Height = 165; Neck = 33; Waist (at navel) = 75; Hip (widest point) = 95.
| Result | Value |
|---|---|
| Estimated body fat | 26.9% |
The first line is the headline result (estimated body fat). IEEE-754 double precision; shown to 1 decimal place unless stated.
How to measure
- Height: standing straight, without shoes.
- Neck: just below the larynx (Adam's apple), tape level and snug.
- Waist: at the navel, relaxed and not pulled in. Some sources suggest the narrowest point for women; this calculator uses the navel.
- Hip (women): at the widest point of the buttocks.
Common mistakes
- Pulling the tape tight or holding the stomach in.
- Using inches in a centimetre form; keep all measurements in the same unit.
- Measuring at a different site each time, which changes the result more than real change in fat does.
How waist size changes the estimate (man, 180 cm, neck 38 cm)
Every figure in this table comes from running this calculator, so it matches what the form returns.
| Waist (cm) | Estimated body fat |
|---|---|
| 75 | 7.6% |
| 85 | 16.1% |
| 95 | 23.2% |
| 105 | 29.4% |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Waist (at navel): entering "38" shows "Waist must be larger than neck." beside that field and no result.
- Hip (widest point): left empty shows "Enter your hip measurement." beside that field and no result.
Choosing between the Body Fat Calculator (U.S. Navy) and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Body Surface Area Calculator](/health/bsa/) | weight and height | Body surface area |
| [Adjusted Body Weight Calculator](/health/adjusted-weight/) | sex, actual weight and height | Adjusted body weight |
| [BMI Calculator](/health/bmi-calculator/) | units, weight and height | Your BMI |
| [Height Calculator](/health/height-calculator/) | convert | Height |
| [Ideal Weight Calculator](/health/ideal-weight-calculator/) | units, sex and height | Ideal weight (Devine) |
Background: body measurements and screening
Body-measurement ratios are screening tools, not diagnoses. BMI ignores body composition and fat distribution, and reviews find waist-to-hip and waist-to-height ratios are useful additions but not clearly better than BMI or waist circumference alone. Where the tape goes matters, so measure at the same sites each time.
Some sources quote a waist-to-hip ratio above 0.8 for women and 0.95 for men as a marker of increased metabolic risk; treat that as a screening flag, and talk to a clinician about what your own numbers mean.
Assumptions and limitations
- Waist must exceed neck (men) or waist + hip must exceed neck (women)
- Not a diagnosis
This calculator gives general information based on published formulas. It is not medical advice, and it cannot account for your health history. Talk to a qualified clinician about decisions that affect your health.
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for waist (at navel) and hip (widest point) to confirm this.
Frequently asked questions
How accurate is the Navy body fat method?
Accuracy is roughly plus or minus 3 to 4 percentage points. It compares reasonably with other methods for people of average build but is not a clinical test.
What does the Body Fat Calculator (U.S. Navy) calculate?
Estimate body fat percentage from tape measurements (U.S. Navy method). It returns Estimated body fat.
What formula does the Body Fat Calculator (U.S. Navy) use?
Men: %BF = 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). Hodgdon–Beckett circumference equations used by the U.S.
What do I need to enter in the body Fat Calculator (U.S. Navy)?
You enter Sex, Height (cm), Neck (cm) and Waist (at navel) (cm). Optional: Hip (widest point) (cm).
How is the result rounded or limited?
IEEE-754 double precision; shown to 1 decimal place unless stated. Waist must exceed neck (men) or waist + hip must exceed neck (women).
What are the limits of this calculator?
Waist must exceed neck (men) or waist + hip must exceed neck (women). Not a diagnosis.
What does the “Sex” option change?
It sets how the body Fat Calculator (U.S. Navy) is worked out. The choices are Male and Female.
What is an example of a body Fat Calculator (U.S. Navy) result?
With sex Male, height 180, neck 38 and waist (at navel) 85, the estimated body fat is 16.1%.
Where does the method come from?
The method follows: Hodgdon JA, Beckett MB, Naval Health Research Center Reports 84-29 and 84-11 (1984).
Can I rely on this calculator for a decision?
This calculator gives general information based on published formulas. It is not medical advice, and it cannot account for your health history. Talk to a qualified clinician about decisions that affect your health. For this calculator in particular: Waist must exceed neck (men) or waist + hip must exceed neck (women).
Related calculators
- BMI Calculator — Find your Body Mass Index (BMI) and weight status.
- Height Calculator — Convert height between centimeters and feet-and-inches.
- Ideal Weight Calculator — Ideal body weight by four published formulas (Devine, Robinson, Miller, Hamwi).
- Waist-to-Hip Ratio Calculator — Waist-to-hip ratio and WHO risk threshold.
- Hair Growth Calculator — How long it takes hair to reach a target length at a growth rate you choose.
Sources
- Hodgdon JA, Beckett MB, Naval Health Research Center Reports 84-29 and 84-11 (1984)
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.