Body Fat Percentage Calculator
Free online body fat calculator. Estimate your body fat percentage using different methods like BMI, Navy Formula, and skinfold measurements.
This body fat calculator helps you estimate your body fat percentage and body composition using three different methods. Choose between the BMI method (simplest), the U.S. Navy method (circumference measurements), or the skinfold method (most accurate). Get a breakdown of your lean body mass and fat mass, along with your body fat category.
How This Tool Works
Our body fat calculator offers three different methods to estimate your body fat percentage:
BMI Method
This method uses the Deurenberg equation which estimates body fat percentage based on BMI, age, and gender:
Body Fat % = (1.20 × BMI) + (0.23 × Age) − (10.8 × Gender) − 5.4
Where Gender = 1 for males and 0 for females
This is the simplest method but also the least accurate, as it doesn't account for muscle mass and body composition.
U.S. Navy Method
This method uses circumference measurements from different body parts to estimate body fat percentage:
For men:
Body Fat % = 495 / (1.0324 - 0.19077 × log10(waist) + 0.15456 × log10(height)) - 450
For women:
Body Fat % = 495 / (1.29579 - 0.35004 × log10(waist) + 0.22100 × log10(height) - 0.15456 × log10(hip)) - 450
This method is more accurate than BMI and only requires basic measurements that can be taken at home with a tape measure.
Skinfold Method (Jackson-Pollock)
This method uses skinfold measurements from three sites to estimate body density, which is then converted to body fat percentage using the Siri equation:
1. Calculate body density using the sum of skinfolds and age
2. Convert to body fat percentage using: Body Fat % = (495 / Body Density) - 450
This is the most accurate method among the three but requires specific equipment (skinfold calipers) and proper technique for taking measurements.
For all methods, the calculator also provides your lean body mass (LBM) and fat mass based on your weight:
- Fat Mass = Weight × (Body Fat % / 100)
- Lean Body Mass = Weight - Fat Mass
Frequently Asked Questions
Which body fat calculation method is most accurate?
Among the three methods offered in this calculator, the skinfold method is generally the most accurate, followed by the Navy method, with the BMI method being the least accurate. However, all these methods are estimates and can have an error margin of 3-8%. For clinical accuracy, methods like DEXA scans (gold standard, 1-2% error), hydrostatic weighing, or air displacement plethysmography (Bod Pod) are preferred. These require specialized equipment available at fitness centers, universities, or medical facilities.
What is a healthy body fat percentage?
Healthy body fat percentage ranges differ significantly between men and women:
- For men: 14-17% is considered the "fitness" range, while 18-24% is "average." Athletes often maintain 6-13%.
- For women: 21-24% is the "fitness" range, while 25-31% is "average." Female athletes typically maintain 14-20%.
It's important to note that some body fat is essential (2-5% for men, 10-13% for women) for normal physiological functions. Falling below these levels can negatively impact health, hormonal balance, and immune function.
How often should I measure my body fat percentage?
For most people tracking fitness progress, measuring body fat percentage once every 4-8 weeks is sufficient. Body composition changes relatively slowly, and more frequent measurements might show normal fluctuations rather than true changes. When tracking body composition during weight loss or muscle-building programs, it's helpful to use consistent measurement timing (same time of day, same hydration status) and method for comparable results. Daily weight fluctuations are often due to water, food, and waste changes rather than actual fat loss or gain.
Why do women naturally have higher body fat percentages than men?
Women naturally maintain higher body fat percentages than men due to biological and hormonal differences related to reproductive functions. Women have higher levels of estrogen, which promotes fat storage, particularly in the hips, thighs, and breasts (essential fat for pregnancy and lactation). This sex-specific fat distribution, often called gynoid or "pear-shaped," is different from the typical android or "apple-shaped" fat distribution in men. Additionally, men generally have more testosterone, which promotes muscle development and helps maintain a lower body fat percentage. These physiological differences explain why healthy body fat percentage ranges are approximately 8-10% higher for women than for men.
Tips and Best Practices
Tips for measuring body fat and improving body composition:
- For Navy method measurements, use a flexible but non-stretching tape measure. Take measurements first thing in the morning before eating or drinking.
- For skinfold measurements, specialized calipers are required. Consider having a professional like a personal trainer take these measurements for better accuracy.
- Consistency in measurement technique is crucial - use the same method, time of day, and (if possible) the same person to take measurements.
- Focus on body fat percentage rather than weight alone, as the scale doesn't differentiate between muscle loss and fat loss.
- For reducing body fat healthily, aim for a gradual approach: moderate calorie deficit (300-500 calories/day), increased protein intake (0.8-1g per pound of body weight), strength training to preserve muscle, and sufficient sleep.
- Remember that extremely low body fat levels (below essential fat) can cause health problems and are not sustainable for most people.
- Consider tracking body measurements (waist, hips, arms, etc.) and progress photos alongside body fat percentage for a more complete picture of changes.
- If you're an athlete or fitness competitor needing precise measurements, consider professional methods like DEXA scans, especially when making important training decisions.