How to calculate body fat percentage
Enter the measurements shown in the form, choose Male or Female, then select Calculate Body Fat %. The calculator converts the entries to centimeters, applies the matching US Navy formula, and shows the percentage, category, formula, and converted values.
How to use the calculator
- Enter a positive value in Height and choose cm, ft, or in.
- Enter positive values in Neck circumference and Waist circumference, choosing cm or in beside each field.
- Choose Male or Female. Female also needs a positive value in Hip circumference.
- Select Calculate Body Fat % to display the percentage and calculation details.
- Select Reset to clear every measurement and hide the result.
What measurements does the calculator use?
The Male formula uses Height, Neck circumference, and Waist circumference. The Female formula also uses Hip circumference. The script reads the values and units from those fields, then applies the formula for the selected Sex.
For example, the Male branch can use the values shown here:
Height: 175 cm
Neck circumference: 38 cm
Waist circumference: 85 cm
Sex: Male
Body fat percentage: 16.9%
Category: FitnessThe displayed percentage is rounded to one decimal place. The category comes from the selected Male or Female category table.
How the calculator converts units
The calculator converts every measurement to centimeters before calculation. Height in ft is multiplied by 30.48. Any measurement in in is multiplied by 2.54. Values entered in cm stay in centimeters.
Male uses waist minus neck. Female uses waist plus hip minus neck. The result area shows these formulas:
Male: BF% = 495 / (1.0324 - 0.19077 x log10(waist - neck) + 0.15456 x log10(height)) - 450
Female: BF% = 495 / (1.29579 - 0.35004 x log10(waist + hip - neck) + 0.22100 x log10(height)) - 450Why a measurement may be rejected
Height, Neck circumference, and Waist circumference must contain finite numbers greater than 0. Female also requires Hip circumference to be greater than 0. The calculator rejects a Waist circumference that is equal to or smaller than Neck circumference.
For Female, Waist circumference plus Hip circumference must be greater than Neck circumference. Missing, non-numeric, non-positive, or unusable values keep the result hidden and show an error.
Changing an input, unit, or Sex hides the current result. Select Calculate Body Fat % again after making a change.
What the result includes
The result table lists the selected Sex and formula variant, each value as entered, each converted centimeter value, the percentage, the category, and the formula. The percentage has one decimal place.
Select Copy result to place the plain-text result on the clipboard. Select Download result (.txt) to save body-fat-percentage-calculator-result.txt. The calculation uses the numbers entered in the page's form; its script has no request that submits those measurements.
When to use another calculator
Use the BMI Calculator for a body-size ratio based on height and weight. Choose Health Calculators to compare the available health calculations.
The Calorie Calculator estimates BMR, maintenance calories, or a daily target from age, sex, activity, and measurements. The Calories Burned Calculator estimates activity calories from body weight, activity, duration, and applicable distance.
Which health calculator matches the task?
Choose the Calorie Calculator for estimated BMR, maintenance calories, or a daily weight goal based on age, sex, activity, and measurements. Use the Calories Burned Calculator for an activity estimate based on body weight, activity, duration, and applicable distance.
Frequently asked questions
How does the body fat percentage calculator work?
It converts the entered measurements to centimeters and applies the US Navy circumference formula for the selected Male or Female option. Female inputs include hip circumference.
What measurements do I need for a body fat estimate?
You need Height, Neck circumference, and Waist circumference. Select Female to add Hip circumference, then enter positive numbers in the units shown beside each field.
Can I calculate body fat percentage in inches?
Yes. Choose in beside each circumference and choose ft or in beside Height. The calculator converts those entries to centimeters before using the formula.
Why is my body fat percentage input invalid?
Calculation stops when a required value is missing, non-numeric, or not positive, or when the waist is not greater than the neck. For Female, waist plus hip must also be greater than the neck.