This calculator uses the "U.S. Navy Method" formula, which is a widely recognized equation developed by the Naval Health Research Center to estimate body fat percentage without the need for expensive equipment like DEXA scans or hydrostatic weighing.
How to Measure Accurately
Height: Measure while standing barefoot against a wall.
Neck: Measure just below the larynx (Adam's apple), sloping slightly downward toward the front.
Waist: For men, measure at the navel level. For women, measure at the narrowest point of the natural waistline.
Hips (Women only): Measure at the widest point of the hips/buttocks.
Interpreting Your Results
Body fat percentage is a better indicator of health and fitness than BMI because it distinguishes between muscle mass and fat mass. Use the table below for general categories:
Category
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%+
Why Body Fat Percentage Matters
Maintaining a healthy body fat percentage reduces the risk of chronic conditions such as Type 2 diabetes, cardiovascular disease, and hypertension. While "Essential Fat" is necessary for hormonal and reproductive functions, excessive "Storage Fat" can lead to metabolic complications. Unlike BMI, which can label a muscular athlete as "overweight," body fat percentage provides a clearer picture of your physical composition.
function toggleHipInput() {
var gender = document.getElementById("gender").value;
var hipGroup = document.getElementById("hip-group");
if (gender === "female") {
hipGroup.style.display = "block";
} else {
hipGroup.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 resultDiv = document.getElementById("bfp-result");
if (!height || !neck || !waist || (gender === "female" && !hip)) {
resultDiv.style.display = "block";
resultDiv.className = "bfp-error";
resultDiv.innerHTML = "Please fill in all measurement fields correctly.";
return;
}
var bfp = 0;
if (gender === "male") {
// Navy formula for men (Metric)
// 495 / (1.0324 – 0.19077 * log10(waist – neck) + 0.15456 * log10(height)) – 450
bfp = 495 / (1.0324 – 0.19077 * Math.log10(waist – neck) + 0.15456 * Math.log10(height)) – 450;
} else {
// Navy formula for women (Metric)
// 495 / (1.29579 – 0.35004 * log10(waist + hip – neck) + 0.22100 * log10(height)) – 450
bfp = 495 / (1.29579 – 0.35004 * Math.log10(waist + hip – neck) + 0.22100 * Math.log10(height)) – 450;
}
if (isNaN(bfp) || bfp <= 0) {
resultDiv.style.display = "block";
resultDiv.className = "bfp-error";
resultDiv.innerHTML = "Calculation error. Please ensure your waist/hip measurements are larger than your neck measurement.";
return;
}
var category = "";
if (gender === "male") {
if (bfp < 6) category = "Essential Fat";
else if (bfp < 14) category = "Athlete";
else if (bfp < 18) category = "Fitness";
else if (bfp < 25) category = "Average";
else category = "Obese";
} else {
if (bfp < 14) category = "Essential Fat";
else if (bfp < 21) category = "Athlete";
else if (bfp < 25) category = "Fitness";
else if (bfp < 32) category = "Average";
else category = "Obese";
}
resultDiv.style.display = "block";
resultDiv.className = "bfp-success";
resultDiv.innerHTML = "Estimated Body Fat: " + bfp.toFixed(1) + "%Category: " + category;
}