Body Fat Calculator
Estimate body fat percentage using the U.S. Navy circumference method.
Result
Fill in the inputs to see your result.
Inputs
How it works
It's an estimate — DEXA scans and bod-pod tests are more accurate, but this method is consistent enough to track changes.
Formula
Uses the U.S. Navy circumference formula based on neck, waist, hip and height.
Common mistakes
- Measuring at the wrong spot — measure waist at the navel, neck below the larynx.
Related calculators
Last updated
Reviewed Apr 15, 2026.
Calcxo gives you the answer plus the reasoning behind it.
Quick answer
Body Fat Calculator: in one paragraph
Body fat percentage estimates how much of your weight is fat versus everything else (muscle, bone, water). The U.S. Navy method uses a few tape measurements; it's a rough but widely used proxy.
What this calculator does
The calculator applies the U.S. Navy circumference formula to your height, neck, waist (and hip, for women) measurements. It returns an estimated body-fat percentage and the matching fitness category.
Why people use it
- Get a quick body-composition signal without calipers or a DEXA scan.
- Track changes during a cut or bulk when the scale alone is misleading.
- Tell muscle gain from fat gain when bodyweight stays flat.
- Sanity-check what BMI is telling you — especially if you train.
A worked body-fat calculation
A concrete walkthrough you can follow line by line.
Man, 180 cm tall, neck 38 cm, waist 84 cm.
1. Tape correctly
Measure neck below the larynx and waist at the navel, relaxed.
2. Apply Navy formula
495 ÷ (1.0324 − 0.19077·log10(waist−neck) + 0.15456·log10(height)) − 450
3. Round to one decimal
≈ 16.4%
Result
Estimated body fat ≈ 16.4% — within the typical 'fitness' range for adult men.
When to use this calculator
- Comparing month-over-month measurements with the same tape and posture.
- Setting a realistic body-composition goal alongside a training plan.
- Avoid for clinical decisions — DEXA, hydrostatic weighing, or BodPod are far more precise.
Common mistakes
- Sucking in or flexing during measurement — both throw off the result by several percent.
- Measuring after a heavy meal or large fluid intake.
- Comparing tape estimates to DEXA or BodPod numbers — they aren't directly comparable.
- Reading a single measurement as a trend; take the average of three on different days.
Quick questions
How accurate is the Navy method?+
Typically within ±3–4% of the value a DEXA scan would give for the same person, when measurements are taken carefully. It's better for tracking change over time than for a one-shot absolute number.
What's a healthy body-fat percentage?+
Common ranges: men 10–20% and women 18–28% are considered healthy. Athletic ranges sit a few points lower; very low values are not sustainable for most people.
Learn more
Deeper reads from the Calcxo learn library.