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Body Fat Calculator.
Estimate body fat percentage using measurements
Set your values
Results update as you type.
US Navy Method
This calculator estimates body fat from your height and a few circumference measurements, using the formula developed for the US Navy. All you need is a tape measure.
Body Measurements
Your Body Composition
Body fat percentage
13.7%Athletic
Fat mass
9.6 kg
Lean mass
60.4 kg
Body Fat Categories
Men
- Essential fat: 2-5%
- Athletic: 6-13%
- Fitness: 14-17%
- Average: 18-24%
- Above average: 25%+
Women
- Essential fat: 10-13%
- Athletic: 14-20%
- Fitness: 21-24%
- Average: 25-31%
- Above average: 32%+
Measurement Tips
- Measure in the morning, before eating and after using the bathroom.
- Keep the tape snug against the skin without compressing it.
- Measure the same spots each time so results stay comparable.
- Take each measurement two or three times and use the average.
- This is an estimate; methods like DEXA scans are more precise.
How to Use the Body Fat Calculator
Estimate your body fat percentage using the U.S. Navy method, which uses body measurements to calculate body composition. This method is more accurate than BMI for assessing actual body fat.
- Select your gender (male or female).
- Enter your weight and height.
- Measure and enter your neck circumference.
- Measure and enter your waist circumference.
- If female, also measure and enter your hip circumference.
- Select your preferred unit system (metric or imperial).
- Review your body fat percentage and category.
Navy Method Body Fat Formulas
The U.S. Navy developed these formulas based on extensive body composition research.
Male Body Fat Formula
Uses waist and neck measurements along with height to estimate body fat.
Example:
Input: Waist: 36 inches, Neck: 15 inches, Height: 70 inches
Calculation: BF% = 495 / (1.0324 - 0.19077 × log₁₀(36 - 15) + 0.15456 × log₁₀(70)) - 450
Result: Approximately 20% body fat
Female Body Fat Formula
Includes hip measurement for women, as fat distribution differs from men.
Example:
Input: Waist: 32 inches, Hip: 38 inches, Neck: 13 inches, Height: 65 inches
Calculation: BF% = 495 / (1.29579 - 0.35004 × log₁₀(32 + 38 - 13) + 0.22100 × log₁₀(65)) - 450
Result: Approximately 22% body fat
Real-World Use Cases
Body fat percentage provides more insight than BMI alone, especially for tracking fitness progress.
Fitness Progress Tracking
Track body composition changes during weight loss or muscle gain programs.
Example: A person may lose weight but gain muscle, improving body fat percentage from 25% to 18%
Athletic Performance
Athletes monitor body fat to optimize performance and body composition.
Example: Endurance athletes typically maintain 6-13% (men) or 14-20% (women) body fat for optimal performance
Health Risk Assessment
Lower body fat percentages are associated with reduced risk of metabolic diseases.
Example: Maintaining body fat below 20% (men) or 30% (women) reduces diabetes and heart disease risk
Muscle Building Programs
Bodybuilders track body fat to ensure they're gaining muscle, not just weight.
Example: A bodybuilder may track body fat decreasing from 15% to 10% while maintaining weight
Medical Monitoring
Healthcare providers use body fat percentage to assess metabolic health.
Example: A doctor may monitor body fat percentage changes in patients with metabolic syndrome
Tips & Best Practices
Tips
- Take measurements in the morning before eating for most consistent results.
- Use a flexible measuring tape and keep it parallel to the ground.
- Measure at the same location each time - waist at navel level, neck at narrowest point.
- Take multiple measurements and average them for accuracy.
- This method is an estimate - DEXA scan or BodPod provide more accurate measurements.
- Track changes over time rather than focusing on a single measurement.
Common Mistakes to Avoid
- Measuring waist too high or too low - should be at navel level.
- Pulling tape too tight or too loose - should be snug but not compressing skin.
- Measuring after a large meal or bloating, which affects waist measurements.
- Not taking measurements consistently at the same time of day.
- Using the calculator for children or teens without age-specific considerations.
Related Resources
Related Calculators
Cite this calculator
Canonical URL: https://mathify.one/en/fitness/body-fat
Cite as: Mathify. (2026). Body Fat Calculator. https://mathify.one/en/fitness/body-fat
Use Cases
Track fitness progress
Regularly measure your body fat percentage to see how your diet and exercise routine are affecting your body composition over time.
Example: Measure monthly and log results to see a downward trend as you lose fat.
Set realistic fitness goals
Use your estimated body fat percentage to set achievable targets based on healthy ranges for your gender and age.
Example: If you're at 25% body fat, aim for 20% as a realistic goal.
Frequently Asked Questions
- How does the Body Fat Calculator estimate body fat percentage?
- This calculator uses simple tape measurements (typically waist, neck, and height for men; waist, hip, neck, and height for women) to estimate body fat percentage. It applies standard formulas like the U.S. Navy method, which are based on anthropometric data and provide a reasonable estimate without needing specialized equipment.
- What measurements do I need to use this calculator?
- You'll need a flexible tape measure. For men, measure your waist and neck circumference, and your height. For women, measure your waist, hip, and neck circumference, and your height. Ensure measurements are taken at the correct anatomical points for accuracy.
- How accurate is this body fat estimate?
- The estimate is a good approximation for most people, but it can vary based on factors like age, fitness level, and body composition. It's not as precise as methods like DEXA scans or hydrostatic weighing. Use it as a tracking tool to monitor trends over time rather than an absolute measure.
Tips & Common Mistakes
Tips
- Take measurements at the same time of day, preferably in the morning before eating or drinking, for consistent results.
- Use a flexible, non-stretchable tape measure and ensure it's snug but not compressing the skin.
- Repeat each measurement twice and take the average to reduce errors.
- Track changes over weeks or months rather than day-to-day, as body fat can fluctuate with hydration and other factors.
Common Mistakes to Avoid
- Measuring over clothing or bulky undergarments, which adds extra circumference and skews results.
- Pulling the tape too tight or too loose, leading to inaccurate measurements.
- Using the wrong anatomical landmarks, such as measuring the waist at the belly button instead of the narrowest point.
Last updated: August 13, 2026