Body Fat Calculator
Estimate your body fat percentage, fat mass and lean mass
Results & Details
// Body Composition
// Body Fat Categories
| Category | Men | Your Status |
|---|
// Weight to Reach Next Category
// Method Comparison
How Body Fat Is Calculated
This calculator offers three methods to estimate body fat percentage. Each uses different measurements and has different accuracy characteristics. No home method is as accurate as DEXA scanning or hydrostatic weighing, but these methods provide a useful estimate.
US Navy Method
Uses circumference measurements — waist, neck, and (for women) hips — along with height. It was developed by the US military and is widely used for its ease of measurement. Accuracy is typically within 3–4% of actual body fat.
BMI-Based Estimate
Estimates body fat from BMI, age and sex using a published regression formula. Less accurate than circumference or skinfold methods, as BMI cannot distinguish muscle from fat, but useful when circumference measurements are not available.
Jackson-Pollock 3-Site Skinfold
Uses caliper measurements at three skinfold sites. For men: chest, abdomen, thigh. For women: tricep, suprailiac, thigh. This method can be very accurate (within 2–3%) when performed consistently by a trained practitioner.
Body Fat Percentage: The Number BMI Can't Give You
Built and verified by Andrius R. · Updated June 2026
Body fat percentage answers the question BMI dodges: how much of your weight is fat versus everything else (muscle, bone, organs, water). Two people can share a height and weight — identical BMI — and have completely different compositions and health pictures.
How the Navy method works
A man, 180 cm tall, waist 90 cm, neck 38 cm:
BF% = 495 ÷ [1.0324 − 0.19077·log₁₀(waist − neck) + 0.15456·log₁₀(height)] − 450 = ~19.8%
(Women's version adds the hip measurement.) The logic: waist size tracks fat, neck size tracks frame/lean mass, and the formula was calibrated against underwater weighing on thousands of service members. With careful tape placement it lands within ~3–4% of lab methods for most physiques — enough to classify you correctly and, more importantly, to track change over time.
What the ranges mean (ACE classification)
| Category | Men | Women |
|---|---|---|
| Essential fat | 2–5% | 10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obesity | 25%+ | 32%+ |
Women's healthy ranges run ~8–10 points higher than men's — essential fat for hormonal and reproductive function, not something to train away. Chasing magazine-cover leanness year-round is neither realistic nor healthy for either sex.
How the measurement methods compare
- Tape/Navy method (this calculator): free, repeatable, ±3–4%. Its real strength is trend tracking.
- Bioimpedance scales (BIA): convenient but swing with hydration — the same body can read several points apart morning vs evening. Weigh the trend, not single readings.
- Skinfold calipers: ±3–5%, heavily dependent on the tester's skill.
- DEXA scan: the practical gold standard (±1–2%), typically $50–150 — worth it for a calibration point, overkill for routine tracking.
The honest takeaway: every consumer method has error bars wider than a week of progress. Measure the same way, same time of day, same conditions — and judge by the 4–8-week trend.
Why location beats percentage
Where fat sits matters as much as how much there is. Visceral fat — packed around the abdominal organs — is far more strongly linked to cardiovascular and metabolic risk than subcutaneous fat under the skin. This is why waist circumference appears in clinical screening even when body fat percentage doesn't: a simple check is keeping your waist under half your height. A person with a "fine" body fat percentage but a thickening waistline still has a finding worth acting on.
Changing the number
Body fat percentage has two inputs — fat mass and lean mass — so it improves from both directions: a moderate calorie deficit (size it with our calorie calculator) reduces the numerator, while resistance training with adequate protein (~1.6–2.2 g per kg of body weight) protects or grows the denominator. Dieting without training loses muscle along with fat, which is how people end up lighter but with nearly the same body fat percentage — the "skinny fat" outcome the scale alone never warns you about.
From the Blog
// Accuracy Order
DEXA > Hydrostatic > Air displacement > Skinfold > Navy circumference > BMI. No home method matches lab testing.
// Measure Consistently
For tracking trends, always measure at the same time of day (morning, fasted) and use the same method each time.
// Essential Fat
Essential fat (3–5% men, 10–13% women) is necessary for organ function. Going below this is dangerous.
// Muscle Matters
Losing fat while preserving lean mass is the goal. Track both fat mass and lean mass, not just the percentage.