U.S. Navy Body Fat Calculator
Accurately estimate your body composition using the Navy Fitness formula
Gender
Male
Female
Height (cm)
Neck (cm)
Waist (cm)
Hips (cm) (Required for females)
Calculate Body Fat %
How the Body Fat Calculator Works
The U.S. Navy Body Fat Calculator uses a formula developed by the Naval Health Research Center to estimate the percentage of total body weight that is fat. Unlike BMI (Body Mass Index), which only considers height and weight, this method accounts for body circumference measurements, providing a more accurate assessment of lean body mass vs. fat tissue.
How to Measure Correctly
Height: Measure standing upright without shoes.Neck: Measure just below the larynx (Adam's apple), sloping the tape slightly downward to the front.Waist:
Men: Measure horizontally at the navel.
Women: Measure at the narrowest part of the abdomen (usually above the navel).
Hips (Women only): Measure at the widest horizontal circumference of the buttocks.
Navy Method Formulas
The calculator uses the following metric equations:
Men: 495 / (1.0324 – 0.19077 * log10(waist – neck) + 0.15456 * log10(height)) – 450Women: 495 / (1.29579 – 0.35004 * log10(waist + hip – neck) + 0.22100 * log10(height)) – 450
Ideal Body Fat 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%+
Example Calculation: A 180cm male with a 90cm waist and 40cm neck would have approximately 18.2% body fat, placing him in the "Average" category.
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 resultBox = document.getElementById("result-box");
var bfValue = document.getElementById("bf-value");
var bfCategory = document.getElementById("bf-category");
var bfDescription = document.getElementById("bf-description");
if (!height || !neck || !waist || (gender === "female" && !hip)) {
alert("Please fill in all required fields with valid numbers.");
return;
}
var bodyFatPercent = 0;
if (gender === "male") {
// U.S. Navy Formula for Men (Metric)
// 495 / (1.0324 – 0.19077 * log10(waist – neck) + 0.15456 * log10(height)) – 450
var val = 1.0324 – (0.19077 * Math.log10(waist – neck)) + (0.15456 * Math.log10(height));
bodyFatPercent = (495 / val) – 450;
} else {
// U.S. Navy Formula for Women (Metric)
// 495 / (1.29579 – 0.35004 * log10(waist + hip – neck) + 0.22100 * log10(height)) – 450
var val = 1.29579 – (0.35004 * Math.log10(waist + hip – neck)) + (0.22100 * Math.log10(height));
bodyFatPercent = (495 / val) – 450;
}
if (isNaN(bodyFatPercent) || bodyFatPercent 60) {
alert("The calculation resulted in an unrealistic value. Please check your measurements.");
return;
}
var category = "";
var desc = "";
if (gender === "male") {
if (bodyFatPercent < 6) { category = "Essential Fat"; desc = "This level is necessary for physiological function."; }
else if (bodyFatPercent < 14) { category = "Athlete"; desc = "Very lean, common for endurance athletes."; }
else if (bodyFatPercent < 18) { category = "Fitness"; desc = "A healthy, fit appearance."; }
else if (bodyFatPercent < 25) { category = "Average"; desc = "Standard body fat range for men."; }
else { category = "Obese"; desc = "High risk for cardiovascular issues and metabolic disease."; }
} else {
if (bodyFatPercent < 14) { category = "Essential Fat"; desc = "This level is necessary for reproductive and hormonal health."; }
else if (bodyFatPercent < 21) { category = "Athlete"; desc = "Very lean, common for female athletes."; }
else if (bodyFatPercent < 25) { category = "Fitness"; desc = "A healthy, athletic physique."; }
else if (bodyFatPercent < 32) { category = "Average"; desc = "Standard body fat range for women."; }
else { category = "Obese"; desc = "High risk for cardiovascular issues and metabolic disease."; }
}
bfValue.innerHTML = bodyFatPercent.toFixed(1) + "%";
bfCategory.innerHTML = category;
bfDescription.innerHTML = desc;
resultBox.style.display = "block";
resultBox.scrollIntoView({ behavior: 'smooth', block: 'center' });
}