Body Fat Calculator
Estimate your body fat percentage using multiple evidence‑based methods (U.S. Navy, YMCA, BMI-based and skinfold). Get instant classification and reference charts by age and sex.
1. Your details
2. Results
Primary estimate (Navy method)
— %
Category: —
Bar scaled 0–50%. Values above 50% are capped visually.
Estimated fat mass
— kg
Estimated lean mass
— kg
Show all methods
Navy method: %
YMCA method: —%
BMI-based estimate: —%
Skinfold (Jackson–Pollock): —%
Note: Methods may differ. Use trends over time rather than a single absolute number.
Disclaimer: This tool provides estimates only and is not a medical diagnosis. Discuss results with your healthcare professional.
What is body fat percentage?
Body fat percentage is the proportion of your total body weight that is made up of fat tissue. It includes both essential fat (needed for normal physiological function) and storage fat (energy reserves in adipose tissue).
Compared with BMI, body fat percentage is a more direct indicator of body composition because it distinguishes between fat mass and lean mass (muscle, bone, organs, water).
How this body fat calculator works
This calculator combines several widely used field methods to estimate body fat percentage:
- U.S. Navy method – based on height, neck, waist, and hip (for women).
- YMCA method – based on weight, waist, and wrist.
- BMI-based estimate – uses BMI and age to approximate body fat.
- Skinfold (Jackson–Pollock) – optional if you have caliper measurements.
The primary result shown is the Navy method, because it is practical and reasonably accurate for many adults when measurements are taken carefully.
1. U.S. Navy body fat formula
The U.S. Navy method uses logarithms of circumference measurements. All lengths must be in centimeters.
For men:
\( \text{BF%} = 495 \big/ \left[1.0324 - 0.19077 \cdot \log_{10}(\text{waist} - \text{neck}) + 0.15456 \cdot \log_{10}(\text{height})\right] - 450 \)
For women:
\( \text{BF%} = 495 \big/ \left[1.29579 - 0.35004 \cdot \log_{10}(\text{waist} + \text{hip} - \text{neck}) + 0.22100 \cdot \log_{10}(\text{height})\right] - 450 \)
2. YMCA body fat formula (simplified)
The YMCA method relates waist circumference to body weight. Here we use a commonly cited linear approximation:
Men (waist in cm, weight in kg):
\( \text{BF%} \approx 0.74 \cdot \text{waist} - 0.082 \cdot \text{weight} - 44.74 \)
Women:
\( \text{BF%} \approx 0.74 \cdot \text{waist} - 0.082 \cdot \text{weight} - 34.89 \)
Different YMCA variants exist; all are approximations and can over‑ or underestimate in individuals with atypical fat distribution.
3. BMI-based body fat estimate
Several research equations relate BMI and age to body fat percentage. A commonly used one is:
Deurenberg equation:
\( \text{BF%} = 1.20 \cdot \text{BMI} + 0.23 \cdot \text{age} - 10.8 \cdot S - 5.4 \)
where \( S = 1 \) for males and \( S = 0 \) for females.
and \( \text{BMI} = \dfrac{\text{weight (kg)}}{\text{height (m)}^2} \).
This method is quick but less precise for very muscular or very lean individuals, because BMI does not distinguish between fat and muscle.
4. Skinfold (Jackson–Pollock) estimate
If you enter the sum of skinfolds (in mm), the calculator uses a simplified Jackson–Pollock style equation:
Example approximation (men):
\( \text{BF%} \approx 0.29288 \cdot \text{SF} - 0.0005 \cdot \text{SF}^2 + 0.15845 \cdot \text{age} - 5.76377 \)
where SF is the sum of selected skinfold sites in millimeters.
In practice, different equations are used depending on the exact sites and number of measurements (3‑site, 7‑site, etc.). Accuracy depends heavily on the skill of the person using the calipers.
How we classify your body fat percentage
The calculator assigns a category based on sex‑specific cut‑offs adapted from common reference charts (e.g., American Council on Exercise and clinical sources). Ranges are approximate and may vary slightly between organizations.
Typical body fat categories for adults
| Category | Men | Women |
|---|---|---|
| Essential fat | ~2–5% | ~10–13% |
| Athletes | 6–13% | 14–20% |
| Fitness | 14–17% | 21–24% |
| Average | 18–24% | 25–31% |
| Obese | ≥ 25% | ≥ 32% |
These ranges are for adults. Children, adolescents, pregnant people, and older adults may have different reference values.
Body fat percentage by age (approximate)
Body fat tends to increase with age even if weight stays similar. The table below shows approximate “healthy” ranges often cited in the literature:
| Age | Men (healthy) | Women (healthy) |
|---|---|---|
| 20–29 | 8–18% | 18–28% |
| 30–39 | 11–20% | 19–30% |
| 40–49 | 13–22% | 21–32% |
| 50–59 | 15–24% | 22–33% |
| 60+ | 17–26% | 23–35% |
Ranges compiled from multiple sources (e.g., ACSM, clinical reviews). They are guidelines, not strict cut‑offs.
How to take accurate measurements
For the most reliable estimates:
- Measure in front of a mirror or ask someone you trust to help.
- Stand relaxed, feet hip‑width apart, breathing out gently (do not suck in your stomach).
- Use a flexible, non‑stretch measuring tape and keep it horizontal around the body.
Key sites for this calculator
- Waist: At the level of the navel (belly button) or the narrowest part of the torso.
- Hip (women): Around the widest part of the buttocks.
- Neck: Just below the larynx (Adam’s apple), tape slightly downward at the front.
- Wrist (YMCA): At the narrowest point above the wrist bone.
- Skinfolds: Follow the protocol for your specific 3‑ or 7‑site method if using calipers.
Limitations and safety notes
- Online body fat calculators are estimation tools, not diagnostic devices.
- Accuracy can be reduced in people with very high or very low body fat, unusual fat distribution, or significant muscle mass (e.g., strength athletes).
- Hydration status, recent meals, and measurement technique can all affect results. Focus on trends over time rather than single readings.
- If you have a medical condition, are pregnant, or are considering major weight changes, discuss goals and measurements with a healthcare professional.