Estimate your body composition using the U.S. Navy Method.
Male
Female
How Does the Body Fat Calculator Work?
This calculator uses the U.S. Navy Body Circumference Method, which is one of the most widely used and scientifically validated equations for estimating body fat without expensive clinical equipment like DEXA scans or hydrostatic weighing. By measuring specific points on the body, the formula estimates the volume of lean mass versus adipose tissue.
The Formulas Used
The math behind the calculation differs based on gender to account for biological differences in fat storage patterns:
Let's look at a realistic scenario for a male user:
Height: 72 inches (6'0″)
Neck: 16 inches
Waist: 36 inches
Using the formula: 86.010 * log10(36 – 16) – 70.041 * log10(72) + 36.76.
The result would be approximately 18.5%, placing this individual in the "Average" fitness category.
Tips for Accuracy
Measure on bare skin: Fabric adds bulk and skews results.
Don't pull too tight: The tape should be snug against the skin but not indenting it.
Measure in the morning: Stay consistent by measuring at the same time, preferably before eating.
Neck: Measure just below the larynx (Adam's apple).
Waist: Measure at the narrowest point for women or at the navel for men.
function toggleHips() {
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 resultDiv = document.getElementById("bf-result");
if (isNaN(height) || isNaN(neck) || isNaN(waist) || height <= 0 || neck <= 0 || waist <= 0) {
resultDiv.style.display = "block";
resultDiv.style.backgroundColor = "#f8d7da";
resultDiv.style.color = "#721c24";
resultDiv.innerHTML = "Error: Please enter valid positive numbers for all fields.";
return;
}
var bodyFat = 0;
if (gender === "male") {
// Navy Formula for Men: 86.010 * log10(waist – neck) – 70.041 * log10(height) + 36.76
var diff = waist – neck;
if (diff <= 0) {
resultDiv.innerHTML = "Error: Waist must be larger than neck.";
resultDiv.style.display = "block";
return;
}
bodyFat = 86.010 * Math.log10(diff) – 70.041 * Math.log10(height) + 36.76;
} else {
// Navy Formula for Women: 163.205 * log10(waist + hips – neck) – 97.684 * log10(height) – 78.387
var hips = parseFloat(document.getElementById("hips").value);
if (isNaN(hips) || hips <= 0) {
resultDiv.innerHTML = "Error: Please enter a valid hip measurement.";
resultDiv.style.display = "block";
return;
}
var total = waist + hips – neck;
if (total <= 0) {
resultDiv.innerHTML = "Error: Invalid measurements for formula.";
resultDiv.style.display = "block";
return;
}
bodyFat = 163.205 * Math.log10(total) – 97.684 * Math.log10(height) – 78.387;
}
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";
}
resultDiv.style.display = "block";
resultDiv.style.backgroundColor = "#d4edda";
resultDiv.style.color = "#155724";
resultDiv.innerHTML = "