Estimate your body composition using the U.S. Navy Method
Male
Female
Metric (cm/kg)
Imperial (in/lb)
Your Estimated Body Fat
0.0%
Category
Body Fat Percentage: Understanding Your Health Metrics
While total body weight is a common metric, body fat percentage is a far more accurate indicator of fitness and overall health. Your body fat percentage tells you what portion of your total weight is comprised of fat versus lean mass (muscle, bone, organs, and water).
What is the Navy Method?
The U.S. Navy Method is a formula developed by the Naval Health Research Center to estimate body fat percentage. It relies on circumference measurements and height rather than expensive equipment like DEXA scans or hydrostatic weighing. While it has a margin of error of about 3-4%, it is highly accessible for tracking progress over time.
How to Measure Correctly
Neck: Measure just below the larynx (Adam's apple), with the tape sloping slightly downward to the front.
Waist (Men): Measure horizontally around the navel. Do not suck in your stomach.
Waist (Women): Measure at the narrowest point of the natural waistline (usually above the navel).
Hips (Women only): Measure the largest horizontal circumference of the buttocks.
Height: Measure without shoes, standing straight against a flat wall.
Body Fat Categories (ACE Standards)
Description
Women
Men
Essential Fat
10-13%
2-5%
Athletes
14-20%
6-13%
Fitness
21-24%
14-17%
Average
25-31%
18-24%
Obese
32%+
25%+
Example Calculation
A male standing 180cm tall with a 90cm waist and 40cm neck would calculate his body fat as follows:
It is a reliable estimate for the general population. However, it may overestimate fat in very muscular individuals (bodybuilders) or underestimate it in those with low muscle mass ("skinny fat").
How often should I measure?
Because body fat changes slower than water weight, measuring once every 2-4 weeks is sufficient to track a weight loss or muscle gain trend.
function toggleHipField() {
var gender = document.getElementById('bf-gender').value;
var hipContainer = document.getElementById('hip-container');
if (gender === 'female') {
hipContainer.style.display = 'block';
} else {
hipContainer.style.display = 'none';
}
}
function calculateBF() {
var gender = document.getElementById('bf-gender').value;
var units = document.getElementById('bf-units').value;
var h = parseFloat(document.getElementById('bf-height').value);
var n = parseFloat(document.getElementById('bf-neck').value);
var w = parseFloat(document.getElementById('bf-waist').value);
var hip = parseFloat(document.getElementById('bf-hip').value) || 0;
if (!h || !n || !w || (gender === 'female' && !hip)) {
alert("Please fill in all required fields with valid numbers.");
return;
}
// Convert to metric if imperial
var height = (units === 'imperial') ? h * 2.54 : h;
var neck = (units === 'imperial') ? n * 2.54 : n;
var waist = (units === 'imperial') ? w * 2.54 : w;
var hips = (units === 'imperial') ? hip * 2.54 : hip;
var bodyFat = 0;
if (gender === 'male') {
// Navy Formula for Men: 495 / (1.0324 – 0.19077 * log10(waist – neck) + 0.15456 * log10(height)) – 450
bodyFat = 495 / (1.0324 – 0.19077 * Math.log10(waist – neck) + 0.15456 * Math.log10(height)) – 450;
} else {
// Navy Formula for Women: 495 / (1.29579 – 0.35004 * log10(waist + hip – neck) + 0.22100 * log10(height)) – 450
bodyFat = 495 / (1.29579 – 0.35004 * Math.log10(waist + hips – neck) + 0.22100 * Math.log10(height)) – 450;
}
if (bodyFat < 2) bodyFat = 2; // Bottom floor for essential fat
displayResults(bodyFat, gender);
}
function displayResults(bf, gender) {
var resultBox = document.getElementById('bf-result-box');
var bfText = document.getElementById('bf-percentage');
var catText = document.getElementById('bf-category');
var idealText = document.getElementById('bf-ideal');
resultBox.style.display = 'block';
bfText.innerText = bf.toFixed(1) + "%";
var category = "";
var color = "";
if (gender === 'male') {
if (bf < 6) { category = "Essential Fat"; color = "#3498db"; }
else if (bf < 14) { category = "Athlete"; color = "#27ae60"; }
else if (bf < 18) { category = "Fitness"; color = "#2ecc71"; }
else if (bf < 25) { category = "Average"; color = "#f1c40f"; }
else { category = "Obese"; color = "#e74c3c"; }
idealText.innerText = "Ideal range for men (Fitness/Athlete): 6-17%";
} else {
if (bf < 14) { category = "Essential Fat"; color = "#3498db"; }
else if (bf < 21) { category = "Athlete"; color = "#27ae60"; }
else if (bf < 25) { category = "Fitness"; color = "#2ecc71"; }
else if (bf < 32) { category = "Average"; color = "#f1c40f"; }
else { category = "Obese"; color = "#e74c3c"; }
idealText.innerText = "Ideal range for women (Fitness/Athlete): 14-24%";
}
catText.innerText = category;
catText.style.color = color;
resultBox.scrollIntoView({ behavior: 'smooth', block: 'center' });
}