Body Fat Calculator

For a measurement you can do at home with a $5 tape measure, it's remarkably good — typically within 3–4% of a DEXA scan for most adults. Accuracy is best in the middle of the body-fat range (roughly 12–30%) and drops at the extremes, where waist, neck, and hip circumferences don't capture body composition as cleanly. It's not as precise as DEXA or hydrostatic weighing, but it's the most accurate no-equipment method available.

Calipers require practice to use consistently — most people can't replicate their own measurements within 2–3% site-to-site. A tape measure is unambiguous: wrap it at the specified location, read the number. The Navy formula was specifically designed to work with circumferences because the military needed a field-deployable method that any instructor could apply with consistent results.

Neck: just below the larynx (Adam's apple), tape angled slightly downward, standing relaxed — don't flex. Waist: men measure at the navel level; women measure at the narrowest point, usually just above the navel. Hip (women only): the largest circumference around the hips and glutes, feet together. Keep the tape snug but not compressing the skin, and take each measurement twice — if they differ by more than half an inch, measure again.

Men: 6–17% is the athletic/fitness range, 18–24% is average, 25%+ is classified as obese. Women: 14–24% is athletic/fitness, 25–31% is average, 32%+ is obese. Essential fat (minimum for health) is 2–5% for men, 10–13% for women — don't target levels that low without medical supervision.

Women carry a higher baseline of essential fat (around breasts, hips, thighs) for hormonal and reproductive function, so the same waist-to-neck ratio reflects different total body fat. The women's formula adds hip circumference to capture that distribution. Applying the men's formula to a woman would underestimate by roughly 6–10%.

Bodyweight is fine for rough progress tracking, but body fat percentage is what actually tells you whether you're losing fat vs. muscle. Two people at identical weight and height can look completely different: one at 25% body fat is soft, one at 12% is athletic. If your scale weight is stuck but your waist is shrinking, you're recomping — body fat dropping, muscle mass holding or growing.

Ninety percent of the time it's a measurement issue. Re-measure your waist standing relaxed (not flexed, not sucking in) and at the correct anatomical point. Double-check you're reading the tape at the same level all the way around — a tape that rides up in the back inflates the number. If two independent measurements still give the same surprising result, the formula's probably right and the result just disagrees with what you expected.

Every 2–4 weeks is enough. Measuring more often just adds noise — day-to-day variation from sodium, water, and food volume can shift your waist by half an inch either direction without any change in body fat. Take measurements first thing in the morning, after using the bathroom, before eating or drinking, for the most consistent read.