Body Fat Percentage Calculator
The US Navy circumference method — surprisingly decent accuracy from nothing but a tape measure.
Estimate your body fat %
How the Navy method works
Developed for fleet-wide fitness testing, the US Navy method estimates body fat from circumference measurements — waist and neck for men, plus hips for women — and height. Validation studies put it within roughly 3–4 percentage points of lab methods for most physiques: not lab-grade, but remarkable for a $3 tape measure, and excellent for tracking change over time.
Measuring correctly (this is where accuracy lives)
Waist: at the navel, relaxed — not sucked in, not pushed out. Neck: just below the larynx, tape sloping slightly down in front. Hips (women): at the widest point. Measure in the morning, before eating, tape snug but not compressing skin, and take each measurement twice. Consistency matters more than perfection: same time, same spots, every few weeks.
Reading the number honestly
Typical reference bands (ACE): men — athletes 6–13%, fitness 14–17%, average 18–24%; women — athletes 14–20%, fitness 21–24%, average 25–31%. Women carry more essential fat by design; that's biology, not a flaw. Two cautions: single readings wobble with hydration and measurement technique, so trust the trend across weeks, and very lean targets (sub-10% men, sub-18% women) are competition territory with real hormonal costs, not year-round health goals. If you're making body-composition decisions for health reasons, loop in a doctor or dietitian.
Frequently asked questions
How accurate is this versus a DEXA scan?
DEXA is the gold standard; the Navy method typically lands within 3–4 points of it. Where it drifts: very muscular necks read leaner, and fat carried atypically can skew either way. For tracking monthly change, it's genuinely useful.
Why does my smart scale say something different?
Bioimpedance scales are highly sensitive to hydration and can swing several points in a day. Neither method is exact — pick one, use it consistently, and watch the trend rather than comparing devices.
What's a healthy body fat percentage?
Broadly: men ~10–20%, women ~18–28%, with athletic and average bands inside those. Health risk concentrates at the extremes — very high, and aggressively low maintained year-round.
How fast can body fat percentage change?
Sustainably, expect roughly 0.5–1 point per month with a moderate deficit, adequate protein, and resistance training. Faster scale loss is usually water and muscle, which defeats the purpose.
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How body fat percentage is estimated — the two main methods on this calculator
This calculator uses two evidence-based methods for estimating body fat percentage without requiring expensive equipment:
US Navy Method: Developed at the Naval Health Research Center. Uses height, weight, waist circumference, and neck circumference (plus hip circumference for women). Formula for men: %BF = 495 ÷ (1.0324 − 0.19077 × log10(waist − neck) + 0.15456 × log10(height)) − 450. For women: %BF = 495 ÷ (1.29579 − 0.35004 × log10(waist + hip − neck) + 0.22100 × log10(height)) − 450. Accuracy: within 1–3% of DEXA scan for most individuals.
BMI Method (Deurenberg formula): Uses BMI, age, and sex to estimate body fat: %BF = (1.20 × BMI) + (0.23 × age) − (10.8 × sex) − 5.4, where sex = 1 for male, 0 for female. Less accurate than the Navy method but requires only a scale and measuring tape for height and weight.
Body fat percentage categories
Men: Essential fat 2–5%, athletes 6–13%, fitness 14–17%, acceptable 18–24%, obese 25%+.
Women: Essential fat 10–13%, athletes 14–20%, fitness 21–24%, acceptable 25–31%, obese 32%+.
Women carry higher essential fat due to sex-hormone-related fat stores. These categories come from the American Council on Exercise (ACE).
Accuracy and the gold standard comparison
The most accurate body fat measurement methods, ranked: DEXA scan (dual-energy X-ray absorptiometry) — the gold standard, within ±1%. Hydrostatic weighing (underwater weighing) — within ±2%, historically considered gold standard. Air displacement plethysmography (BOD POD) — within ±2–3%. Navy tape method — within ±3–4% in most populations, best for field use. Bioelectrical impedance (BIA) — varies wildly with hydration; consumer scales with BIA can be ±5–8% or more. BMI-based estimates — within ±5%, least accurate but requires only a scale.
Worked examples with real numbers
Example 1 — Man, 5'10", 185 lb, 33" waist, 15" neck: Navy method: approximately 18% body fat. Category: fitness/acceptable border. The healthy range for men of this height and frame suggests waist circumference below 36" is the clearer metabolic health indicator than the body fat number alone.
Example 2 — Woman, 5'6", 145 lb, 29" waist, 38" hips, 13" neck: Navy method: approximately 26% body fat. Category: acceptable. Body fat reduction of 3–5% (to ~21–23%) would move this person into the fitness category — achievable with 6–9 months of consistent resistance training and moderate caloric adjustment.
Frequently asked questions
Which body fat method is most accurate?
DEXA scan is the gold standard — within ±1% for most people and it measures regional fat distribution (trunk, limb, visceral). For at-home estimation, the Navy tape method is the most reliable, with accuracy within ±3–4% for most individuals. Bioelectrical impedance (the technology in most consumer smart scales) is convenient but highly sensitive to hydration — a single body fat reading from a BIA scale can vary 5–8% depending on when you ate, drank, or exercised.
Is body fat percentage better than BMI?
For most individuals, yes. BMI does not distinguish muscle from fat and misclassifies muscular people as overweight. Body fat percentage directly measures what you actually want to know. However, for population health screening, BMI is simpler and correlates well with outcomes in aggregate. For individual assessment — particularly athletes or anyone doing strength training — body fat percentage is the more meaningful metric.
How can I lower my body fat percentage?
Body fat reduction requires a sustained caloric deficit — consuming fewer calories than you expend over time. Resistance training is critical: it preserves and builds muscle during a deficit, improving the fat-to-muscle ratio at the same body weight. High protein intake (0.7–1.0g per pound of body weight) further protects muscle during weight loss. The math: 3,500 calorie deficit ≈ 1 lb of fat. A 500-calorie daily deficit = approximately 1 lb/week of fat loss. See the Calorie Needs Calculator.
How accurate is the Navy body fat method?
The Navy method has been validated against hydrostatic weighing and DEXA and produces results within ±3–4% for most people. It is most accurate for people with typical body proportions and least accurate for very muscular individuals (tends to underestimate fat), people with unusual fat distribution, and the very elderly. For the purposes of tracking change over time — rather than absolute measurement — it is highly reliable because the same systematic bias applies consistently to your measurements.
What is visceral fat and why does it matter?
Visceral fat is fat stored around internal organs (liver, intestines, pancreas) rather than under the skin (subcutaneous fat). It is metabolically active, releasing inflammatory cytokines and contributing to insulin resistance, cardiovascular disease, and type 2 diabetes — independently of total body fat. Waist circumference is the practical proxy for visceral fat: men over 40 inches and women over 35 inches carry elevated cardiometabolic risk. Body fat percentage calculators do not directly measure visceral fat — DEXA provides regional breakdown.
Disclaimer: Body fat estimates from this calculator are approximations based on population-level equations. Individual accuracy varies. These are not medical assessments. Consult a physician or registered dietitian for personalized body composition evaluation and guidance.