Frequently Asked Questions

Online calculators using the U.S. Navy method are typically accurate within ±3-4%. Skinfold-based methods like Jackson-Pollock are accurate within ±2-3%. BMI-derived estimates have the widest error margins (±5%+). All methods are best used for tracking trends over time.

The U.S. Navy method uses circumference measurements (neck, waist, and hips for women) along with height to estimate body fat. It was developed by Hodgdon and Beckett at the Naval Health Research Center. For men: 86.010 × log10(waist - neck) - 70.041 × log10(height) + 36.76 (all in cm).

At minimum you need: sex, age, height, weight, neck circumference, and waist circumference. Women also need hip circumference. For the more accurate Jackson-Pollock method, you'll need skinfold calipers to measure three sites.

For men: 2-5% is essential fat (minimum for survival), 6-13% is athletic, 14-17% is fitness, 18-24% is average/acceptable, and 25%+ is above average. Most health benefits are seen below 20%. Essential fat levels are not sustainable long-term.

For women: 10-13% is essential fat, 14-20% is athletic, 21-24% is fitness, 25-31% is average/acceptable, and 32%+ is above average. Women carry more essential fat for reproductive and hormonal health. Most health benefits are seen below 30%.

Measure at the level of your navel (belly button), keeping the tape level around your body. Stand relaxed, don't suck in your stomach. Measure directly on skin or over a thin shirt. Take the measurement at the end of a normal exhale.

Measure just below the larynx (Adam's apple), with the tape sloping slightly downward at the front. Keep the tape snug but not tight. Look straight ahead and keep your shoulders relaxed.

Each method measures different body properties and uses different mathematical models. Circumference methods estimate fat from body shape, skinfolds measure subcutaneous fat directly, and BMI-derived formulas use statistical averages. No single formula is perfect for everyone.

Every 2-4 weeks is ideal for tracking progress. Body fat changes slowly, so more frequent measurements mainly capture water weight fluctuations. Always measure under the same conditions (time of day, hydration, same measurement technique) for consistency.

No. BMI (Body Mass Index) is a ratio of weight to height that doesn't distinguish between muscle and fat. A muscular person can have a high BMI but low body fat. Our BMI-derived body fat estimate uses the Deurenberg equation to approximate body fat from BMI, but it's the least accurate method especially for muscular or very lean individuals.

You need a skinfold caliper — available for $10-30 online. Consistent technique matters more than caliper brand. Take each measurement 2-3 times and use the average. Having someone else take measurements (especially for hard-to-reach sites) improves accuracy.

The gold standard methods are: DEXA scan (±1-2%), hydrostatic weighing (±1-2%), and BodPod/air displacement (±2-3%). These require specialized equipment and typically cost $50-150 per session. For home tracking, the Navy method with consistent technique provides reliable trend data.