Estimate your body fat percentage using the U.S. Navy Method
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Female
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Understanding the U.S. Navy Body Fat Formula
The U.S. Navy Body Fat Calculator provides an estimate of body composition by using specific circumference measurements. Unlike BMI (Body Mass Index), which only considers height and weight, this method accounts for where you carry your mass, offering a better distinction between muscle and fat.
How the Calculation Works
The algorithm uses logarithmic equations developed by the Naval Health Research Center. The requirements differ based on biological sex:
For Men: Measurements of height, neck, and waist (at the navel) are required.
For Women: Measurements of height, neck, waist (at the narrowest point), and hips (at the widest point) are required.
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%+
Accuracy and Tips for Measurement
To get the most accurate result from this body fat calculator, follow these measurement protocols:
Waist: Measure at the horizontal level of the navel for men, and at the smallest neck of the abdomen for women. Do not suck in your stomach.
Neck: Measure below the larynx, sloping slightly downward to the front.
Hips (Women only): Measure at the widest horizontal point of the buttocks.
Consistency: Measure at the same time of day, preferably in the morning before eating.
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 weight = parseFloat(document.getElementById("weight").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 resultBox = document.getElementById("result-box");
var bfOutput = document.getElementById("bf-output");
var catOutput = document.getElementById("cat-output");
var massOutput = document.getElementById("mass-output");
if (!weight || !height || !neck || !waist || (gender === "female" && !hip)) {
alert("Please enter all required measurements.");
return;
}
var bodyFatPercent = 0;
if (gender === "male") {
// Navy formula for men: 86.010*log10(waist-neck) – 70.041*log10(height) + 36.76
bodyFatPercent = 86.010 * Math.log10(waist – neck) – 70.041 * Math.log10(height) + 36.76;
} else {
// Navy formula for women: 163.205*log10(waist+hip-neck) – 97.684*log10(height) – 78.387
bodyFatPercent = 163.205 * Math.log10(waist + hip – neck) – 97.684 * Math.log10(height) – 78.387;
}
if (isNaN(bodyFatPercent) || bodyFatPercent <= 0) {
alert("Please check your measurements. The resulting calculation is invalid.");
return;
}
var bfFinal = bodyFatPercent.toFixed(1);
var fatMass = (weight * (bodyFatPercent / 100)).toFixed(1);
var leanMass = (weight – parseFloat(fatMass)).toFixed(1);
bfOutput.innerHTML = bfFinal + "%";
resultBox.style.display = "block";
resultBox.style.backgroundColor = "#f0fdf4";
resultBox.style.border = "1px solid #bbf7d0";
var category = "";
var catColor = "";
if (gender === "male") {
if (bodyFatPercent < 6) { category = "Essential Fat"; catColor = "#3b82f6"; }
else if (bodyFatPercent < 14) { category = "Athlete"; catColor = "#22c55e"; }
else if (bodyFatPercent < 18) { category = "Fitness"; catColor = "#16a34a"; }
else if (bodyFatPercent < 25) { category = "Average"; catColor = "#ca8a04"; }
else { category = "Obese"; catColor = "#dc2626"; }
} else {
if (bodyFatPercent < 14) { category = "Essential Fat"; catColor = "#3b82f6"; }
else if (bodyFatPercent < 21) { category = "Athlete"; catColor = "#22c55e"; }
else if (bodyFatPercent < 25) { category = "Fitness"; catColor = "#16a34a"; }
else if (bodyFatPercent < 32) { category = "Average"; catColor = "#ca8a04"; }
else { category = "Obese"; catColor = "#dc2626"; }
}
catOutput.innerHTML = category;
catOutput.style.color = catColor;
massOutput.innerHTML = "Fat Mass: " + fatMass + " lbs | Lean Mass: " + leanMass + " lbs";
window.scrollTo({
top: resultBox.offsetTop – 100,
behavior: 'smooth'
});
}