Health & Body Composition
Body Fat Method Comparison
Different body-fat methods disagree by design. Enter one set of measurements and see what all four methods say.
Body-fat methods disagree: the Navy circumference formula, YMCA waist-and-weight formula, FFMI lean-mass index, and skinfold calipers each estimate differently. Comparing them on the same measurements shows the spread — typically ±3–5%. Results are screening estimates, not diagnoses — confirm with a clinician before acting on them.
One measurement set → 4 estimates.
Expect ±3–5% spread between methods.
Trust trends within one method over time.
Calculate Your Body Fat Method Comparison
Midpoint Estimate
What Is Body Fat Method Comparison?
Every body-fat method measures something slightly different, which is why your scale, your calipers, and the Navy formula rarely agree to the decimal point.
This tool runs the two most common tape formulas — Navy and YMCA — on the same measurements, derives the FFMI lean-mass index, and shows the spread. The midpoint is the fairest single estimate; the trend within one method is the fairest measure of change.
How It Is Calculated
Navy: 495 ÷ (1.0324 − 0.19077·log10(W−N) + 0.15456·log10(H)) − 450 (men)
YMCA: 4.15·waist(in) − 0.082·weight(lb) − 98.42 (men)
FFMI: lean mass ÷ height²
Example: Example: 80 kg man, 85 cm waist, 38 cm neck, 178 cm → Navy 17.1% · YMCA 17.2% · FFMI 20.9
The four home methods compared
| Method | Inputs | Typical error |
|---|---|---|
| Navy circumference | Waist, neck, height (+hips) | ±3–4% |
| YMCA formula | Waist + weight | ±4–5% |
| Skinfold (3-site) | Calipers, 3 sites | ±3–4% |
| DEXA (lab) | Full scan | ±1–2% |
Limitations
- Home methods are ±3–5% — the spread you see here is that error made visible.
- Consistency beats accuracy: same method, same conditions, same tester.
- DEXA remains the reference standard where available.
Sources & Review
References used for this calculator’s formulas and thresholds:
Body Fat Method Comparison FAQ
Which body fat method is most accurate at home?
The Navy circumference method (±3–4%) edges out YMCA, and skinfold with a skilled tester is comparable. The midpoint of two methods is your safest single number.
Why do my scale and calipers disagree?
They measure different things — impedance vs subcutaneous fat vs circumference — and each carries its own error. A ±3–5% spread is normal.
Which method should I track?
One method, consistently. The trend over 8–12 weeks is the real signal; switching methods breaks the series.
Important disclaimer: Results are educational estimates, not a substitute for professional medical advice. Discuss your results with a qualified professional before making decisions.