Body Fat Calculator
Estimate your body fat percentage using the US Navy, BMI-based, or skinfold method and find your body composition category.
| Category | Men | Women |
|---|---|---|
| Essential Fat | 2–5% | 10–13% |
| Athletic | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Acceptable | 18–24% | 25–31% |
| Obese | ≥25% | ≥32% |
Estimate your body fat percentage from simple tape-measure circumferences using the U.S. Navy method, and see your fat mass, lean mass, and body composition category.
How Body Fat Calculator Works
The Navy method estimates body fat from circumference measurements rather than weight alone. For men, the formula is 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76; for women it adds hip circumference: 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387. All measurements are converted to centimeters before the calculation runs, regardless of which unit you entered them in.
A separate BMI-based formula is offered as an alternative when tape measurements aren't available: body fat % = 1.20 × BMI + 0.23 × age − 10.8 × (1 for men, 0 for women) − 5.4. It is less precise than the Navy method since it doesn't account for where fat is distributed on the body.
Once body fat percentage is known, fat mass and lean mass are split from your total weight, and the result is placed into a category (essential fat, athletic, fitness, acceptable, or obese) with separate ranges for men and women, since healthy fat percentages differ by sex.
See It In Action
Who Uses Body Fat Calculator and Why
- Getting a body composition estimate at home without access to a DEXA scan or hydrostatic weighing.
- Tracking body fat percentage changes over a training block alongside weight, since weight alone can't show whether you're losing fat or muscle.
- Comparing the tape-measure Navy method against the simpler BMI-based estimate when you don't have all the circumference measurements handy.
Mistakes to Avoid
- Measuring waist, neck, or hip loosely or over clothing — the Navy method's log-based formula is sensitive to small measurement errors, so an inch of slack in the tape changes the result noticeably.
- Comparing a Navy-method result against a BMI-based estimate from another source and assuming one is wrong — the two formulas use different inputs and are expected to diverge somewhat, especially for atypical body shapes.
- Measuring at different times of day (e.g. right after a meal vs. first thing in the morning) between check-ins, which adds noise to the comparison.
Tips for Best Results
- Measure at the same time of day, using the same tape tension, each time you retest — consistency in technique matters more than getting one single measurement perfectly precise.
- Track the trend over several weeks rather than reacting to any single reading, since the tape-measure method has more day-to-day noise than a lab method like DEXA.
Fixing Common Problems
My body fat percentage seems unusually low or high for how I look. — Re-measure carefully — waist should be measured at the navel and neck just below the larynx, without pulling the tape too tight or leaving it loose. A half-inch error in waist or neck can shift the estimate by a few percentage points.
The Navy method and BMI-based estimate gave very different results. — This is expected for people with an atypical build — very muscular or very lean individuals tend to see more disagreement between the two formulas, since the BMI-based version doesn't account for fat distribution.
Terms Explained
Lean mass: Everything in your body besides fat — muscle, bone, organs, and water — calculated here by subtracting estimated fat mass from total weight.
Essential fat: The minimum body fat needed for basic physiological function, roughly 2-5% for men and 10-13% for women.