This tool is for informational purposes only and does not constitute medical advice. Always consult a healthcare professional.
How the Body Fat Calculator Works
This body fat calculator uses the US Navy circumference method, which estimates body fat percentage from simple tape measurements. For men, the formula requires height, waist circumference, and neck circumference. For women, it additionally requires hip circumference to account for gender-specific fat distribution patterns. The method uses logarithmic calculations to convert these measurements into an estimated body fat percentage.
The US Navy method was developed for military fitness assessments and provides a practical way to estimate body fat without expensive equipment like DEXA scanners or hydrostatic weighing tanks. While not as precise as laboratory methods, it is generally accurate within 3-4% for most individuals and is widely used in fitness and health assessments around the world.
How to Use This Tool
- Select your gender — this determines which formula variant is used and whether hip measurement is required.
- Enter your height — type your height in centimetres.
- Enter your waist measurement — measure at the narrowest point (typically at navel level) in centimetres.
- Enter your neck measurement — measure just below the larynx in centimetres.
- For women: enter hip measurement — measure at the widest point of the buttocks in centimetres.
How It Works Behind the Scenes
The US Navy formula for men is: Body Fat % = 86.010 x log10(waist - neck) - 70.041 x log10(height) + 36.76. For women: Body Fat % = 163.205 x log10(waist + hip - neck) - 97.684 x log10(height) - 78.387. All measurements are in centimetres. The logarithmic approach accounts for the non-linear relationship between body circumferences and actual fat content.
The fat mass is calculated by multiplying body fat percentage by total body weight. Lean mass is total weight minus fat mass. The body fat category is determined by comparing the calculated percentage against established ranges that differ for men and women, with categories spanning from essential fat through athlete, fitness, acceptable, and obese levels.
Frequently Asked Questions
What is the US Navy body fat method?
The US Navy method estimates body fat percentage using simple circumference measurements taken with a tape measure. For men, it uses waist and neck measurements along with height. For women, it additionally requires a hip measurement. The formula uses logarithmic calculations to convert these circumferences into a body fat estimate. It was developed by the US Navy for fitness assessments and is considered reasonably accurate for most people.
How do I measure my waist, neck, and hips?
Measure your waist at the narrowest point of your natural waistline, typically at the level of your navel, while standing relaxed. Measure your neck just below the larynx (Adam's apple) with the tape sloping slightly downward at the front. For women, measure hips at the widest point of the buttocks. Use a soft measuring tape, keep it snug but not compressing the skin, and measure in centimetres.
What are healthy body fat percentages?
For men: essential fat is 2-5%, athletes typically have 6-13%, fitness level is 14-17%, acceptable is 18-24%, and above 25% is considered obese. For women: essential fat is 10-13%, athletes are 14-20%, fitness level is 21-24%, acceptable is 25-31%, and above 32% is considered obese. Women naturally carry more essential body fat than men due to hormonal and reproductive functions.
How accurate is the US Navy body fat formula?
The US Navy method is generally accurate within about 3-4 percentage points of the true body fat percentage for most individuals. It is less accurate for very lean individuals (such as competitive bodybuilders), very obese individuals, or those with unusual body proportions. More precise methods include DEXA scans, hydrostatic weighing, and air displacement plethysmography. The Navy method's main advantage is that it requires only a tape measure.
Why do women need a hip measurement?
Women store body fat differently from men, with a significantly greater proportion carried around the hips, buttocks, and thighs. The female version of the US Navy formula includes hip circumference to account for this gender-specific fat distribution pattern. Without the hip measurement, the formula would systematically underestimate or overestimate body fat for women. This additional measurement significantly improves the accuracy of the estimate.
Is my data stored?
No. All calculations are performed entirely in your browser using JavaScript. Your body measurements and calculated results are never transmitted to any server or stored in any database. Once you close or refresh the page, all entered data is gone. Daytics is committed to protecting your privacy, particularly with sensitive body measurement data, and operates all tools completely client-side.
