Body Fat Calculator
Example: 86 cm waist, 38 cm neck, 178 cm height = ~17% body fat
Estimate your body fat percentage using the U.S. Navy circumference method. This calculator uses your height, waist, neck, and hip measurements (for women) to calculate body fat. Understanding your body composition helps you set realistic fitness goals and track progress beyond just weight.
Calculation results updated
Body composition
Body Fat Percentage
Category
Lean Mass
Share of body weight that is lean (non-fat) mass
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How We Calculate This
This calculator uses the U.S. Navy circumference method developed by Hodgdon and Beckett in 1984, with all measurements in inches (metric entries are converted first). For men: %BF = 86.010×log10(waist-neck) - 70.041×log10(height) + 36.76. For women: %BF = 163.205×log10(waist+hip-neck) - 97.684×log10(height) - 78.387. Men measure the waist at the navel; women measure it at the narrowest point of the abdomen and add a hip measurement at the widest point. Lean mass is 100 minus the body fat percentage. Category bands follow the American Council on Exercise classification.
Methodology last reviewed: September 2026. How SparkCalc works
Sources: Potter et al. 2022, Frontiers in Physiology: Navy circumference equations (Hodgdon and Beckett 1984) checked against DXA in a U.S. Marine Corps survey (PMC) · American Council on Exercise: body fat percentage averages and dangerously low thresholds for men and women
Frequently Asked Questions
How accurate is the Navy body fat formula?
In a 2022 U.S. Marine Corps survey the Navy equations were checked against DXA scans. They read about 2.5 percentage points low for men and 1 to 2 points high for women, with a typical spread of roughly 4 points either way. Careful measuring matters: between experienced observers the estimate repeats to within about 1 point.
What is a healthy body fat percentage?
The American Council on Exercise puts the average non-athlete at 18-24% for men and 25-31% for women. Its fitness band is 14-17% for men and 21-24% for women, and athletes usually sit at 6-13% and 14-20%. Essential fat is 2-5% for men and 10-13% for women; ACE describes anything below 6% for men or 14% for women as dangerously low.
How do I measure my waist correctly?
The Navy protocol differs by sex. Men measure at navel level; women measure at the narrowest part of the abdomen, and also take the hips at the widest point of the buttocks. Both measure the neck just below the larynx. Stand relaxed, do not pull in your stomach, and keep the tape snug without compressing the skin.
Why does a larger neck mean lower body fat?
The Navy formula uses (waist - neck) because a thicker neck relative to waist typically indicates more muscle mass. Developed neck and trapezius muscles are associated with overall muscularity. The formula captures the ratio of fat-storing areas (waist, hips) to muscle-indicating areas (neck).
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This calculator provides estimates for educational purposes only. Results vary based on individual factors. Consult a healthcare professional for personalized advice.