Body Fat Calculator
Estimate your body fat percentage using the U.S. Navy circumference method. Enter height, waist, neck, and hip measurements for an accurate body composition estimate.
This free online body fat calculator provides instant results with no signup required. All calculations run directly in your browser — your data is never sent to a server. Enter your values below and see results update in real time as you type. Perfect for everyday calculations, homework, or professional use.
Measure at navel level
Measure just below the larynx
Required for females; enter 0 for males
How to Use This Calculator
Enter your input values
Fill in all required input fields for the Body Fat Calculator. Most fields include unit selectors so you can work in your preferred unit system — metric or imperial, whichever matches your problem.
Review your inputs
Double-check that all values are correct and that you have selected the right units for each field. Incorrect units are the most common source of calculation errors and can produce results that are off by factors of 2, 10, or more.
Read the results
The Body Fat Calculator instantly computes the output and displays results with units clearly labeled. All calculations happen in your browser — no loading time and no data sent to a server.
Explore parameter sensitivity
Try adjusting individual input values to see how the output changes. This is a quick and effective way to develop intuition about how different parameters influence the result and to identify which inputs have the largest effect.
Formula Reference
Body Fat Calculator Formula
See calculator inputs for the governing equation
Variables: All variables and their units are labeled in the calculator interface above. Input fields accept values in multiple unit systems — select your preferred unit from the dropdown next to each field.
When to Use This Calculator
- •Use the Body Fat Calculator for personal health tracking and wellness monitoring, establishing a baseline and tracking changes over time.
- •Use it when recording fitness metrics to track progress toward health or athletic goals.
- •Use it to compare measurements before and after a lifestyle, diet, or training change to quantify the impact.
- •Use it as a conversation starter before a doctor's appointment, bringing objective data to discuss with a healthcare professional.
About This Calculator
The Body Fat Calculator is a free health and wellness calculation tool designed for personal use and general informational purposes. Estimate your body fat percentage using the U.S. Navy circumference method. Enter height, waist, neck, and hip measurements for an accurate body composition estimate. This calculator provides reference values based on established health screening formulas and should not be used as a substitute for professional medical advice, diagnosis, or treatment. Results may vary based on individual factors not captured by the calculation. Consult a qualified healthcare provider for personalized health guidance. All calculations are performed locally in your browser — no personal health data is transmitted or stored.
About Body Fat Calculator
The Body Fat Calculator estimates your body fat percentage using the U.S. Navy circumference method, a well-validated technique that requires only a tape measure. Body fat percentage is a more meaningful indicator of health and fitness than weight alone, as it distinguishes between lean mass (muscle, bone, organs) and adipose tissue. Athletes, military personnel, and health-conscious individuals use body fat percentage to track fitness progress, set realistic goals, and assess metabolic health risks. This calculator implements the Hodgdon-Beckett equations developed by the Naval Health Research Center, which correlate closely with hydrostatic weighing results.
The Math Behind It
Formula Reference
U.S. Navy Method (Male)
BF% = 86.010 * log10(waist - neck) - 70.041 * log10(height) + 36.76
Variables: waist, neck, height in cm
U.S. Navy Method (Female)
BF% = 163.205 * log10(waist + hip - neck) - 97.684 * log10(height) - 78.387
Variables: waist, hip, neck, height in cm
Worked Examples
Example 1: Male Body Fat
178 cm tall male, 85 cm waist, 38 cm neck
Body fat is approximately 23.0% — 'Average' range for males.
Example 2: Female Body Fat
165 cm tall female, 75 cm waist, 32 cm neck, 100 cm hips
Body fat is approximately 29.5% — 'Average' range for females.
Common Mistakes & Tips
- !Measuring waist at the wrong location — use navel level for the Navy method, not the narrowest point.
- !Pulling the tape too tight or leaving it too loose. The tape should be snug but not compressing the skin.
- !For females, forgetting to include hip circumference.
- !Comparing body fat percentages across different measurement methods — they can give different numbers for the same person.
Related Concepts
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Frequently Asked Questions
How accurate is the Navy body fat method?
The U.S. Navy method is accurate within 3-4% of hydrostatic weighing for most people. It tends to be more accurate for individuals with average body compositions and may have larger errors for very lean or very obese individuals.
What is a healthy body fat percentage?
For men, 14-24% is considered average/healthy. For women, 21-31% is average/healthy. Athletes typically have lower body fat (6-13% for men, 14-20% for women). Essential fat is 2-5% for men and 10-13% for women.
Can I use inches instead of centimeters?
This calculator uses centimeters. If you have measurements in inches, multiply by 2.54 to convert before entering.