Body fat percentage is a much more accurate health metric than Body Mass Index (BMI). While BMI only considers your total weight relative to your height, body fat percentage identifies exactly how much of that weight is fat versus lean muscle mass, bone, and water.
How the U.S. Navy Method Works
This calculator uses the U.1. Navy Fitness Formula, a scientifically validated method for estimating body composition without expensive laboratory equipment like DEXA scans. It relies on specific circumference measurements to calculate the volume of the body and estimate body density.
Measurement Guide
Neck: Measure below the larynx (Adam's apple), keeping the tape horizontal.
Waist: For men, measure at the navel. For women, measure at the narrowest point of the natural waistline.
Hips (Women only): Measure at the widest point of the buttocks.
Height: Measure without shoes, standing straight against a wall.
Body Fat Categories
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%+
function toggleHipInput() {
var gender = document.getElementById("gender").value;
var hipContainer = document.getElementById("hip-container");
if (gender === "female") {
hipContainer.style.display = "block";
} else {
hipContainer.style.display = "none";
}
}
function calculateBodyFat() {
var gender = document.getElementById("gender").value;
var height = parseFloat(document.getElementById("height").value);
var neck = parseFloat(document.getElementById("neck").value);
var waist = parseFloat(document.getElementById("waist").value);
var hip = parseFloat(document.getElementById("hip").value);
var resultArea = document.getElementById("result-area");
var fatOutput = document.getElementById("fat-percentage-output");
var categoryOutput = document.getElementById("category-output");
if (isNaN(height) || isNaN(neck) || isNaN(waist) || (gender === "female" && isNaN(hip))) {
alert("Please enter all required measurements correctly.");
return;
}
var bodyFat = 0;
if (gender === "male") {
// U.S. Navy Formula for Men (Metric)
// 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 {
// U.S. Navy Formula for Women (Metric)
// 495 / (1.29579 – 0.35004 * log10(waist + hip – neck) + 0.22100 * log10(height)) – 450
bodyFat = 495 / (1.29579 – 0.35004 * (Math.log10(waist + hip – neck)) + 0.22100 * (Math.log10(height))) – 450;
}
if (bodyFat < 2) bodyFat = 2; // Floor for physical possibility
var roundedFat = bodyFat.toFixed(1);
var category = "";
if (gender === "male") {
if (bodyFat < 6) category = "Essential Fat";
else if (bodyFat < 14) category = "Athletes";
else if (bodyFat < 18) category = "Fitness";
else if (bodyFat < 25) category = "Average";
else category = "Obese";
} else {
if (bodyFat < 14) category = "Essential Fat";
else if (bodyFat < 21) category = "Athletes";
else if (bodyFat < 25) category = "Fitness";
else if (bodyFat < 32) category = "Average";
else category = "Obese";
}
fatOutput.innerHTML = roundedFat + "% Body Fat";
categoryOutput.innerHTML = "Category: " + category;
resultArea.style.display = "block";
}