Transparent method
The formula
Worked example
Example inputs
How to interpret the result
The Navy circumference method estimates body fat from a handful of tape-measure readings, and small measurement inconsistencies, exactly where the tape sits, how tight it's pulled, move the result more than people expect for a method this simple. A single reading is a rough estimate, useful mainly as a starting point rather than a precise number to act on.
Before you rely on it
What to check
Track the trend across several measurements taken the same way each time, rather than treating one reading as a precise, final figure.
The common error
Where people go wrong with body fat percentage calculator
Comparing a single reading against a strict target number as if it were lab-grade precise. Tape placement and tension shift the result enough that trend over weeks tells a more reliable story than any one measurement.
Sensitivity evidence
How waist circumference changes the estimated body fat
| Waist circumference | Estimated body fat | Estimated lean body mass |
|---|---|---|
| 27 | 2.0% | 166.6 |
| 31 | 12.4% | 148.9 |
| 34worked example | 18.8% | 138 |
| 37 | 24.3% | 128.7 |
| 41 | 30.6% | 118 |
Every input, tested
Which input moves the estimated body fat most
| Input | Tested from | To | Estimated body fat at each end | Swing |
|---|---|---|---|---|
| Waist circumference | 31 | 37 | 12.4% to 24.3% | 11.9% (63%) |
| Sex | Male | Female | 18.8% to 32.2% | 13.4% (71%) |
| Neck circumference | 14 | 17 | 20.8% to 14.7% | 6.1% (32%) |
| Height | 60 | 74 | 22.2% to 15.8% | 6.4% (34%) |
| Weight | 153 | 187 | 18.8% to 18.8% | none |
| Hip circumference | 36 | 44 | 18.8% to 18.8% | none |
Two variables at once
Estimated body fat by waist circumference and neck circumference
| Waist circumference \ Neck circumference | 12 | 15 | 18 |
|---|---|---|---|
| 27 | 10.0% | 2.0% | 2.0% |
| 31 | 18.8% | 12.4% | 4.7% |
| 34 | 24.3% | 18.8% | 12.4% |
| 37 | 29.1% | 24.3% | 18.8% |
| 41 | 34.6% | 30.6% | 26.0% |
Step by step
The worked example, input by input
| Input | Value used | What it means |
|---|---|---|
| Sex | Male | Used because the Navy method uses different circumference terms by sex. |
| Weight | 170 | Body weight in pounds. |
| Waist circumference | 34 | Measured at the navel, in inches. |
| Neck circumference | 15 | Measured below the larynx, in inches. |
| Hip circumference | 40 | Measured at the widest point. Used for women only. |
| Height | 67 | Height in inches. |
| Estimated body fat | 18.8% | |
| Estimated lean body mass | 138 | |
Inputs, definitions and assumptions
Sex
Used because the Navy method uses different circumference terms by sex.
Weight
Body weight in pounds.
Waist circumference
Measured at the navel, in inches.
Neck circumference
Measured below the larynx, in inches.
Hip circumference
Measured at the widest point. Used for women only.
Height
Height in inches.
Where the inputs come from
The US Navy method uses circumference measurements taken with a flexible tape. Measure the waist at the navel for men, or at the narrowest point for women, the neck below the larynx, and for women the hips at the widest point. Keep the tape snug but not compressing the skin, measure standing relaxed, and take each measurement two or three times and average. Height and weight are also needed. Use the same technique each time so changes are comparable.
When the result stops applying
Circumference formulas are estimates with an error of several percentage points compared with DEXA scans or hydrostatic weighing. Tape placement, body shape and bloating change the result. The method is less accurate for very lean or very heavy people. It says nothing about where fat is deposited beyond the waist, and it is not a medical diagnosis.
What to compare it with
Compare with the lean body mass calculator, which uses a different formula, and see the BMI and waist-to-hip ratio pages for other screens. The BMR and TDEE calculators use body weight for energy needs. For a more accurate reading, a DEXA scan or a professional assessment is the reference.
People also ask
Frequently asked questions
How accurate is the Navy body fat method?
It is usually within a few percentage points of more precise methods for average bodies, but errors are larger for very lean or very heavy people and depend on how carefully you measure.
What is a healthy body fat percentage?
It varies with age and sex, but roughly 10% to 25% for men and 20% to 32% for women is a common healthy range, with athletes lower.
How often should I measure?
Every two to four weeks under the same conditions, since daily changes from water and food are bigger than real changes.