Body Fat Calculator
Estimate your body fat percentage using the US Navy method and BMI method.
How to Use This Body Fat Calculator
- Select your gender — the US Navy formula uses different measurements for men and women. Women also need to enter hip circumference.
- Enter your age — used by the BMI-based (Deurenberg) method to account for the fact that body fat percentage increases with age even at the same BMI.
- Enter your measurements — use a flexible tape measure. Measure neck, waist, and hips (women) at the correct landmarks. Tips are in the FAQ below.
- Compare the two methods — the Navy method is generally more accurate than the BMI method, which uses your height and weight rather than direct measurements.
US Navy Body Fat Formula
The US Navy circumference method was developed to give a practical, equipment-free alternative to hydrostatic weighing for military fitness assessments. It uses the relationship between circumference measurements and body density to estimate fat percentage.
Male: 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76
Female: 495 / (1.29579 − 0.35004 × log10(waist+hip−neck) + 0.22100 × log10(height)) − 450
(all measurements in cm; Hodgdon & Beckett 1984)
BMI-Based Body Fat (Deurenberg Formula)
The Deurenberg formula estimates body fat percentage from BMI, age, and gender. It is less accurate than the Navy method because BMI cannot distinguish muscle from fat, but it requires only weight and height:
Body Fat % = (1.2 × BMI) + (0.23 × age) − (10.8 × gender) − 5.4
(gender = 1 for male, 0 for female)
Body Fat Categories
Body fat percentage ranges differ by gender because women naturally carry more essential fat for hormonal and reproductive functions. The following ranges are used by most health and fitness organizations:
| Category | Men | Women |
|---|---|---|
| Essential Fat | 2–5% | 10–13% |
| Athletic | 6–13% | 14–20% |
| Fit | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Above Average | 25%+ | 32%+ |
Fat Mass vs Lean Mass
Knowing your body fat percentage allows you to calculate both your fat mass (the total weight of fat tissue) and your lean body mass (everything that is not fat — muscle, bone, organs, water). These numbers are more informative than total weight alone for tracking fitness progress, because you can gain muscle while losing fat and your total weight barely changes.
How to Improve Body Fat Percentage
Reducing body fat requires creating a calorie deficit while preserving muscle mass through adequate protein intake (0.7–1g per pound of body weight) and resistance training. Cardio exercise burns calories but without resistance training, some of the deficit will come from muscle loss. Conversely, gaining lean mass requires a slight calorie surplus with heavy compound lifting and sufficient protein. A realistic rate of fat loss is 0.5–1% of body weight per week, and muscle gain is typically 1–2 lbs per month for natural lifters.