How to Use the Body Fat Calculator
This calculator estimates body fat percentage using the U.S. Navy Method with metric or imperial measurements, or an alternative BMI-based estimation. Results include body fat percentage, an ACE fitness category, fat mass, and lean body mass. These are estimation methods, not clinical measurements.
Calculation Modes
Navy Method — Metric
Enter gender, height, weight, neck circumference, and waist circumference in metric units. For females, a hip circumference field also appears.
Men: Body Fat % = 495 / (1.0324 + 0.15456 x log10(height) - 0.19077 x log10(waist - neck)) - 450
Women: Body Fat % = 495 / (1.29579 + 0.22100 x log10(height) - 0.35004 x log10(waist + hip - neck)) - 450
Example: Male, 180 cm, 75 kg, neck 38 cm, waist 85 cm
- Gender: Male
- Height: 180
- Weight: 75
- Neck: 38
- Waist: 85
- Body Fat: 16.107
- Category: Fitness
- Fat Mass: 12.08025 kg
- Lean Mass: 62.91975 kg
After calculating, two tables appear:
- Body Fat Breakdown: Body Fat Percentage, Category (color-coded), Fat Mass, Lean Body Mass, Total Weight
- ACE Body Fat Categories: all five categories for men with your current one highlighted
Example: Female, 165 cm, 60 kg, neck 32 cm, waist 72 cm, hip 96 cm
- Gender: Female
- Height: 165
- Weight: 60
- Neck: 32
- Waist: 72
- Hip: 96
- Body Fat: 26.406
- Category: Average
- Fat Mass: 15.8436 kg
- Lean Mass: 44.1564 kg
After calculating, the same two tables appear. The ACE table now shows women's categories and highlights Average.
Navy Method — Imperial
Enter gender, height as feet plus inches, weight in pounds, neck circumference in inches, and waist circumference in inches. For females, a hip circumference field also appears. Height is in inches for the formula.
Men: Body Fat % = 86.010 x log10(waist - neck) - 70.041 x log10(height) + 36.76
Women: Body Fat % = 163.205 x log10(waist + hip - neck) - 97.684 x log10(height) - 78.387
Example: Male, 5 feet 10 inches, 170 lbs, neck 15 inches, waist 34 inches
- Gender: Male
- Height (ft): 5
- Height (in): 10
- Weight: 170
- Neck: 15
- Waist: 34
- Body Fat: 17.5131
- Category: Fitness
- Fat Mass: 29.77227 lbs
- Lean Mass: 140.22773 lbs
After calculating, two tables appear:
- Body Fat Breakdown: Body Fat Percentage, Category (color-coded), Fat Mass, Lean Body Mass, Total Weight
- ACE Body Fat Categories: all five categories for men with your current one highlighted
Example: Female, 5 feet 6 inches, 140 lbs, neck 13 inches, waist 29 inches, hip 38 inches
- Gender: Female
- Height (ft): 5
- Height (in): 6
- Weight: 140
- Neck: 13
- Waist: 29
- Hip: 38
- Body Fat: 26.6093
- Category: Average
- Fat Mass: 37.2530 lbs
- Lean Mass: 102.7470 lbs
After calculating, the same two tables appear. The ACE table now shows women's categories and highlights Average.
BMI Method
A simpler estimation using your BMI, age, gender, and weight. Less accurate than the Navy Method but requires only basic data.
Men: Body Fat % = (1.20 x BMI) + (0.23 x Age) - 16.2
Women: Body Fat % = (1.20 x BMI) + (0.23 x Age) - 5.4
Example: Male, BMI 23, age 30, weight 72 kg
- Gender: Male
- BMI: 23
- Age: 30
- Weight: 72
- Body Fat: 18.3
- Category: Average
- Fat Mass: 13.176 kg
- Lean Mass: 58.824 kg
After calculating, two tables appear:
- Body Fat Breakdown: Body Fat Percentage, Category (color-coded), Fat Mass, Lean Body Mass, Total Weight
- ACE Body Fat Categories: all five categories for men with your current one highlighted
Example: Female, BMI 22, age 28, weight 58 kg
- Gender: Female
- BMI: 22
- Age: 28
- Weight: 58
- Body Fat: 27.44
- Category: Average
- Fat Mass: 15.9152 kg
- Lean Mass: 42.0848 kg
After calculating, the same two tables appear. The ACE table now shows women's categories and highlights Average.
Precision and Notation Settings
Use the settings bar above the tabs to control how results display:
- Decimal places: Adjust from 0 to 16 decimal places (default is 8)
- Notation: Switch between auto, fixed, exponential, and engineering notation (default is auto)
Your decimal places and notation settings save to your browser automatically. When you return to this calculator, your last chosen format loads without needing to adjust it again.
Common Use Cases
Tracking Fitness Progress
You are a 28-year-old male starting a training program. You measure 180 cm, 75 kg, neck 38 cm, waist 90 cm:
- Switch to Navy Method — Metric
- Enter male as Gender
- Enter 180 as Height, 75 as Weight
- Enter 38 as Neck, 90 as Waist
- Body Fat: 19.811963, Category: Average
- Re-measure monthly and use the same mode to track changes
Using Imperial Measurements
You know your stats in inches and pounds:
- Switch to Navy Method — Imperial
- Enter male as Gender
- Height (ft): 5, Height (in): 10, Weight: 170
- Enter 15 as Neck, 34 as Waist
- Body Fat: 17.5131, Category: Fitness
Quick Estimate Without a Tape Measure
You know your BMI from a recent checkup:
- Switch to BMI Method
- Enter male as Gender
- Enter 23 as BMI, 30 as Age, 72 as Weight
- Body Fat: 18.3, Category: Average
Comparing Methods
You want to see how Navy and BMI methods differ:
- Calculate with Navy Method using your measurements
- Switch to BMI Method, enter your BMI and age
- Compare the two percentages in the breakdown tables
Tips for Accurate Calculations
- Measure consistently: take morning measurements before eating, then average two readings
- Waist must be larger than neck: the Navy Method requires waist circumference to exceed neck circumference
- Hip is required for females: the field appears automatically when female is selected in Navy method
- Navy Method is more accurate than BMI: use Navy when you have a tape measure
- BMI Method overestimates for muscular individuals: it cannot distinguish muscle from fat
- Measure at the right spots: neck below the Adam's apple, waist at narrowest point (men) or navel (women), hip at widest point
- Keep the tape level: hold the measuring tape parallel to the floor, snug but not compressing the skin
Troubleshooting
Required
This appears when a field is left empty. Enter a value in all required fields before calculating.
Please select a gender
Gender is required for all calculation modes and affects both the formula and category thresholds.
Height must be positive
Enter a positive height. Zero and negative heights are rejected.
Neck must be positive
Enter a positive neck circumference. All body measurements must be greater than zero.
Waist must be positive
Enter a positive waist circumference. All body measurements must be greater than zero.
Hip measurement required for females
In Navy Method, women must provide a hip circumference. The field appears automatically when female is selected.
Weight must be positive
Enter a positive weight. Zero and negative weights are rejected.
Waist must be larger than neck
The U.S. Navy Method formula requires waist circumference to be greater than neck circumference. Double-check your measurements if you see this error.
BMI must be positive
In BMI Method, enter a positive BMI value. BMI is always a positive number.
Age must be 1-119
In BMI Method, age must be between 1 and 119 years.
Height (feet) cannot be negative
In imperial mode, the feet portion of height cannot be negative.
Height (inches) must be 0-11.9
In imperial mode, inches must be less than 12. Convert excess inches to feet (for example, 5 feet 13 inches should be 6 feet 1 inch).
Invalid measurements
The calculated body fat percentage was zero or negative, which usually means the measurements are inconsistent (for example, waist not much larger than neck). Re-check your tape measurements.
Breakdown tables not appearing
The details section renders after a successful calculation with no validation errors. Check that all required fields are filled and valid, then click Calculate.