Body Fat Calculator
Estimate your body fat percentage using the US Navy tape measure method and BMI-based estimate. Enter your measurements to get your body fat percentage, body fat category, and health insights — all for free.
What Is Body Fat Percentage?
Body fat percentage is the total mass of fat divided by total body mass, expressed as a percentage. It is a more accurate indicator of health and fitness than weight alone because it distinguishes between fat mass and lean body mass (muscle, bone, water, and organs).
This calculator uses two methods to estimate your body fat percentage:
- US Navy Method: A tape-measure based formula developed by the U.S. Navy that uses height, neck, waist, and for women, hip circumference. It has a margin of error of about 3-5% compared to DEXA scans.
- BMI-Based Estimate: A quick estimate using your BMI, age, and gender. Less accurate than the Navy method but useful as a reference.
How Does the Body Fat Calculator Work?
The calculator uses the following formulas:
US Navy Method (Men):
BF% = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76
US Navy Method (Women):
BF% = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387
BMI-Based Estimate:
BF% = 1.20 × BMI + 0.23 × Age − 10.8 × Gender − 5.4 (Gender: 1 = male, 0 = female)
Fat Mass = Weight × (Body Fat % / 100)
Lean Body Mass = Weight − Fat Mass
All measurements are converted to inches for the Navy method formulas, and the BMI estimate uses your BMI calculated from height and weight.
Why Use This Body Fat Calculator?
- Two Methods: Get both the Navy method and BMI-based estimate for comparison.
- Unit Flexibility: Switch between metric and imperial units.
- Detailed Results: See your body fat percentage, category, fat mass, and lean body mass.
- Visual Breakdown: A chart shows your body composition at a glance.
- Free & Private: No registration, no data storage.
Understanding Your Body Fat Category
- Essential Fat (2-5% men, 10-13% women): The minimum fat needed for normal bodily function.
- Athletic (6-13% men, 14-20% women): Typical for competitive athletes.
- Fitness (14-17% men, 21-24% women): Good fitness level.
- Acceptable (18-24% men, 25-31% women): Average healthy range.
- Overweight (25-29% men, 32-38% women): Above healthy range.
- Obese (30%+ men, 39%+ women): Health risks increase significantly.
❓ Body Fat Calculator FAQ
What is body fat percentage?
Body fat percentage is the proportion of your total body weight that is made up of fat tissue. It's a more accurate measure of health and fitness than weight alone.
How accurate is the US Navy body fat method?
The US Navy method has a margin of error of about 3-5% compared to DEXA scans, which are considered the gold standard. It's a practical, non-invasive method that can be done at home with a tape measure.
What is the difference between the Navy method and BMI estimate?
The Navy method uses circumference measurements (neck, waist, hip) and height, while the BMI estimate uses your BMI, age, and gender. The Navy method is generally more accurate because it accounts for body shape and fat distribution.
How do I measure my waist for body fat calculation?
Measure your waist at the narrowest point, typically just above the belly button. For men, measure at the navel level. For women, measure at the narrowest part of the waist. Keep the tape measure snug but not compressing the skin.
How do I measure my neck for body fat calculation?
Measure your neck just below the Adam's apple (larynx), with the tape measure horizontal and snug against the skin. For men, this is typically just below the larynx.
Do women need to measure their hips?
Yes, for the US Navy method, women need to measure their hip circumference at the widest point around the buttocks. This is a key part of the women's formula.
What is a healthy body fat percentage?
Healthy ranges vary by age and gender. For men, 18-24% is considered acceptable; for women, 25-31% is acceptable. Athletes typically have lower percentages (6-13% for men, 14-20% for women).
What is essential body fat?
Essential fat is the minimum amount of body fat needed for normal bodily function. For men, it's about 2-5%; for women, about 10-13%. Below these levels can be unhealthy.
What is the difference between body fat and BMI?
BMI (Body Mass Index) is a ratio of weight to height that doesn't distinguish between fat and muscle. Body fat percentage directly measures fat mass, providing a more accurate picture of body composition.
How does age affect body fat percentage?
Body fat percentage tends to increase with age as muscle mass decreases and metabolism slows. The BMI-based estimate in this calculator includes age as a factor.
What is the difference between fat mass and lean body mass?
Fat mass is the total weight of fat tissue in your body. Lean body mass is everything else — muscle, bone, water, and organs. Maintaining a healthy ratio is important for overall health.
How often should I measure my body fat?
For tracking progress, measure every 2-4 weeks. Body fat changes slowly, so measuring too frequently may not show meaningful changes. Always measure at the same time of day and under similar conditions.
What is visceral fat and how is it different?
Visceral fat is fat stored around internal organs in the abdominal cavity. It's more dangerous than subcutaneous fat (under the skin) because it's linked to higher risks of heart disease and diabetes. This calculator estimates total body fat, not visceral fat specifically.
Can I use this calculator if I'm pregnant?
This calculator is not designed for pregnant women. Pregnancy causes significant changes in body composition that affect the accuracy of these formulas. Consult your healthcare provider for appropriate health assessments.
How do I reduce my body fat percentage?
Reducing body fat involves creating a caloric deficit through diet and exercise. Combine strength training (to preserve muscle mass) with cardiovascular exercise and a balanced diet rich in protein, vegetables, and whole grains.
What is the difference between the Navy method and skinfold calipers?
The Navy method uses simple tape measurements, while skinfold calipers measure the thickness of subcutaneous fat at specific sites (like triceps, abdomen, and thigh). Both are non-invasive methods with similar accuracy levels (3-5% error margin).
How do I convert measurements between metric and imperial?
This calculator automatically converts between metric and imperial units. Simply select your preferred unit system, enter your measurements, and the calculator handles the conversions for you.
Is this calculator suitable for bodybuilders or athletes?
Yes, but keep in mind that athletes and bodybuilders often have higher muscle mass, which can affect the accuracy of the Navy method. The BMI-based estimate is less accurate for highly muscular individuals. Consider using skinfold calipers or DEXA scans for more precise measurements.