Body Fat Calculator
Estimate your body fat percentage using the US Navy circumference method or the BMI-based formula. Compare results across both methods for a more accurate picture of your body composition.
What Is Body Fat Percentage?
Body fat percentage is the proportion of your total body weight that is composed of fat tissue. It includes both essential fat (needed for normal physiological function) and storage fat (energy reserves stored in adipose tissue).
Body fat percentage is a more meaningful indicator of health and fitness than weight or BMI alone, because it distinguishes between fat mass and lean mass (muscle, bone, organs, water).
US Navy Method
The US Navy body fat formula uses circumference measurements at specific body sites along with height to estimate body fat percentage. It was developed by Hodgdon and Beckett in 1984.
Women: BF% = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387
All measurements must be in centimeters for these formulas (the calculator handles unit conversion automatically).
BMI-Based Estimation
The Deurenberg formula estimates body fat from BMI, age, and sex:
Where sex = 1 for males, 0 for females
Body Fat Categories
| Category | Women | Men |
|---|---|---|
| Essential Fat | 10–13% | 2–5% |
| Athletes | 14–20% | 6–13% |
| Fitness | 21–24% | 14–17% |
| Average | 25–31% | 18–24% |
| Obese | > 32% | > 25% |
How to Measure Circumferences
- Waist: Measure at the navel level (belly button) while standing relaxed. Do not suck in your stomach.
- Neck: Measure just below the larynx (Adam's apple), with the tape sloping slightly downward at the front.
- Hip (women only): Measure at the widest point of the buttocks/hips.
- Height: Stand barefoot against a wall, heels together.
Use a flexible, non-elastic measuring tape. Pull snug but not tight. Measure each site twice and average the results.
All Body Fat Measurement Methods
| Method | Accuracy | Cost | Pros | Cons |
|---|---|---|---|---|
| DEXA Scan | ±1–2% | $50–150 | Gold standard, regional breakdown | Requires clinic visit, radiation |
| Hydrostatic Weighing | ±1.5–2.5% | $40–100 | Very accurate | Uncomfortable, requires full submersion |
| Bod Pod | ±2–3% | $40–75 | Quick, non-invasive | Limited availability |
| Skinfold Calipers | ±3–4% | $5–30 | Portable, inexpensive | Technique-dependent |
| BIA Scales | ±3–5% | $20–200 | At-home convenience | Affected by hydration |
| US Navy Method | ±3–4% | Free | Just a tape measure needed | Less accurate for very lean/obese |
| BMI Estimation | ±5–8% | Free | No measurements needed | Doesn't account for muscle |
Healthy Body Fat Ranges
| Age Group | Women (Healthy) | Men (Healthy) |
|---|---|---|
| 20–29 | 16–24% | 7–17% |
| 30–39 | 17–25% | 12–22% |
| 40–49 | 19–28% | 14–24% |
| 50–59 | 22–31% | 16–27% |
| 60+ | 22–33% | 17–28% |
How to Lose Body Fat
- Caloric deficit: Consume 500–750 fewer calories than your TDEE for a safe fat loss rate of 0.5–1 kg per week
- High protein intake: 1.6–2.2 g/kg of body weight preserves muscle during fat loss
- Resistance training: Essential for maintaining muscle mass while in a deficit
- Cardio: Moderate cardio 3–5x/week increases calorie expenditure
- Sleep: 7–9 hours per night supports fat metabolism and hormone regulation
- Realistic timeline: Expect to lose 1–3% body fat per month with consistent effort
Frequently Asked Questions
Which method is more accurate: US Navy or BMI?
The US Navy circumference method is generally more accurate (±3–4%) than the BMI-based estimation (±5–8%) because it uses actual body measurements rather than just weight and height.
Why do women have higher body fat percentages than men?
Women carry more essential fat for reproductive functions, including breast tissue, uterine lining, and hormonal regulation. Essential fat for women is 10–13% compared to 2–5% for men.
Can I have a normal BMI but high body fat?
Yes. This is called "skinny fat" or normal-weight obesity. A person can have a BMI in the normal range (18.5–24.9) but carry excess body fat due to low muscle mass. This is why body fat percentage is a better health indicator than BMI alone.
How often should I measure body fat?
Every 4–8 weeks is ideal. More frequent measurements can be misleading due to daily fluctuations in hydration and measurement variability. Always measure under the same conditions (same time of day, same hydration state).