.calculator-container {
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
max-width: 800px;
margin: 20px auto;
padding: 25px;
border: 1px solid #e1e4e8;
border-radius: 12px;
background-color: #ffffff;
box-shadow: 0 4px 6px rgba(0,0,0,0.05);
}
.calc-header {
text-align: center;
margin-bottom: 25px;
}
.calc-header h2 {
color: #1a202c;
margin-bottom: 10px;
}
.input-group {
margin-bottom: 15px;
}
.input-group label {
display: block;
font-weight: 600;
margin-bottom: 5px;
color: #4a5568;
}
.input-group input, .input-group select {
width: 100%;
padding: 12px;
border: 1px solid #cbd5e0;
border-radius: 6px;
box-sizing: border-box;
font-size: 16px;
}
.btn-calculate {
width: 100%;
background-color: #3182ce;
color: white;
padding: 15px;
border: none;
border-radius: 6px;
font-size: 18px;
font-weight: bold;
cursor: pointer;
transition: background-color 0.2s;
}
.btn-calculate:hover {
background-color: #2b6cb0;
}
#result-area {
margin-top: 25px;
padding: 20px;
border-radius: 8px;
display: none;
}
.result-success {
background-color: #f0fff4;
border: 1px solid #68d391;
color: #22543d;
}
.result-value {
font-size: 24px;
font-weight: 800;
display: block;
margin-top: 10px;
}
.article-content {
margin-top: 40px;
line-height: 1.6;
color: #2d3748;
}
.article-content h3 {
color: #1a202c;
margin-top: 25px;
}
.hidden {
display: none;
}
Gender
Male
Female
Height (inches)
Neck Circumference (inches)
Waist Circumference (inches)
Hips Circumference (inches) – Females Only
Calculate Body Fat %
Your estimated body fat percentage is:
–%
How the Navy Body Fat Calculator Works
The U.S. Navy body fat formula is a widely recognized method for estimating body composition without the need for expensive equipment like DXA scans or hydrostatic weighing. This method utilizes specific circumference measurements and your height to estimate the volume of fat tissue versus lean mass.
The Mathematics Behind the Calculation
The calculation relies on logarithmic equations developed through regression analysis of naval personnel. These formulas differ by gender because men and women tend to store fat in different anatomical regions.
For Men: %Fat = 495 / (1.0324 – 0.19077 * log10(waist – neck) + 0.15456 * log10(height)) – 450For Women: %Fat = 495 / (1.29579 – 0.35004 * log10(waist + hip – neck) + 0.22100 * log10(height)) – 450
Best Practices for Accurate Measurements
To ensure your results are as accurate as possible, follow these measurement guidelines:
Neck: Measure just below the larynx (Adam's apple), pulling the tape tight enough to stay in place without compressing the skin.Waist: For men, measure at the navel. For women, measure at the narrowest point of the abdomen (the natural waistline).Hips (Women only): Measure at the widest point of the buttocks.Height: Measure while standing barefoot against a flat wall.
What Your Results Mean
While body fat requirements vary by age and athletic goal, general health categories for body fat percentages are typically classified as follows:
Essential Fat: 2-5% (Men), 10-13% (Women)Athletes: 6-13% (Men), 14-20% (Women)Fitness: 14-17% (Men), 21-24% (Women)Average: 18-24% (Men), 25-31% (Women)Obese: 25%+ (Men), 32%+ (Women)
function toggleHips() {
var gender = document.getElementById("gender").value;
var hipsContainer = document.getElementById("hips-container");
if (gender === "female") {
hipsContainer.classList.remove("hidden");
} else {
hipsContainer.classList.add("hidden");
}
}
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 resultArea = document.getElementById("result-area");
var resultDisplay = document.getElementById("result-value");
var categoryText = document.getElementById("category-text");
if (isNaN(height) || isNaN(neck) || isNaN(waist) || height <= 0 || neck <= 0 || waist <= 0) {
alert("Please enter valid positive numbers for all fields.");
return;
}
var bodyFat = 0;
if (gender === "male") {
// Male Navy Formula: 495 / (1.0324 – 0.19077 * log10(waist-neck) + 0.15456 * log10(height)) – 450
if (waist <= neck) {
alert("Waist measurement must be larger than neck measurement.");
return;
}
var maleDenom = 1.0324 – (0.19077 * Math.log10(waist – neck)) + (0.15456 * Math.log10(height));
bodyFat = (495 / maleDenom) – 450;
} else {
// Female Navy Formula: 495 / (1.29579 – 0.35004 * log10(waist + hip – neck) + 0.22100 * log10(height)) – 450
var hips = parseFloat(document.getElementById("hips").value);
if (isNaN(hips) || hips <= 0) {
alert("Please enter a valid hip measurement.");
return;
}
if ((waist + hips) <= neck) {
alert("The sum of waist and hips must be larger than the neck measurement.");
return;
}
var femaleDenom = 1.29579 – (0.35004 * Math.log10(waist + hips – neck)) + (0.22100 * Math.log10(height));
bodyFat = (495 / femaleDenom) – 450;
}
if (bodyFat < 0) bodyFat = 0;
resultDisplay.innerText = bodyFat.toFixed(1) + "%";
resultArea.style.display = "block";
resultArea.className = "result-success";
// Determine Category
var cat = "";
if (gender === "male") {
if (bodyFat < 6) cat = "Essential Fat";
else if (bodyFat < 14) cat = "Athlete";
else if (bodyFat < 18) cat = "Fitness";
else if (bodyFat < 25) cat = "Average";
else cat = "Obese";
} else {
if (bodyFat < 14) cat = "Essential Fat";
else if (bodyFat < 21) cat = "Athlete";
else if (bodyFat < 25) cat = "Fitness";
else if (bodyFat < 32) cat = "Average";
else cat = "Obese";
}
categoryText.innerText = "Classification: " + cat;
}