Body fat percentage is a crucial health metric that represents the proportion of your total body weight that is composed of fat. Unlike body mass index (BMI), which only considers height and weight, body fat percentage provides a more accurate picture of your overall body composition and health status. Having a body fat percentage within the healthy range is vital for maintaining good health, preventing chronic diseases, and optimizing physical performance.
Why Measure Body Fat Percentage?
Monitoring your body fat percentage can help you:
Assess your current health status and identify potential risks associated with being overweight or underweight.
Track your progress during weight management or fitness programs.
Set realistic and personalized health goals.
Understand how your diet and exercise routines are impacting your body composition.
How the Calculator Works (The U.S. Navy Method)
This calculator uses the widely recognized U.S. Navy body fat percentage formula, which is a practical method that relies on circumference measurements and gender. It's relatively easy to perform at home without specialized equipment.
Measurements should be taken in centimeters (cm) for circumference and meters (m) for height.
Ensure the tape measure is snug but not digging into the skin.
For women, the hip measurement is crucial.
The 'log10' refers to the base-10 logarithm.
Interpreting Your Results
Healthy body fat ranges vary by age and gender. Generally:
Athletes: Men: 6-13%, Women: 14-20%
Fitness: Men: 14-17%, Women: 21-24%
Average: Men: 18-24%, Women: 25-31%
Obese: Men: 25%+, Women: 32%+
It's important to remember that these are general guidelines. Consult with a healthcare professional for personalized advice based on your individual health profile.
Example Calculation
Let's calculate for a male:
Height: 1.75 meters
Weight: 80 kg (Note: Weight isn't directly used in the U.S. Navy formula itself, but is important context for overall health and for other body fat estimation methods.)
Disclaimer: This calculator is for informational purposes only and should not be considered a substitute for professional medical advice. Always consult with a qualified healthcare provider for any health concerns or before making any decisions related to your health or treatment.
function calculateBodyFat() {
var bodyWeight = parseFloat(document.getElementById("bodyWeight").value);
var height = parseFloat(document.getElementById("height").value);
var neckCircumference = parseFloat(document.getElementById("neckCircumference").value);
var waistCircumference = parseFloat(document.getElementById("waistCircumference").value);
var hipCircumference = parseFloat(document.getElementById("hipCircumference").value);
var gender = document.getElementById("gender").value;
var resultDiv = document.getElementById("result");
var resultValueDiv = resultDiv.querySelector(".value");
var resultLabelDiv = resultDiv.querySelector(".label");
// Check for valid number inputs
if (isNaN(bodyWeight) || isNaN(height) || isNaN(neckCircumference) || isNaN(waistCircumference) || height <= 0 || neckCircumference <= 0 || waistCircumference <= 0) {
resultValueDiv.textContent = "Error";
resultLabelDiv.textContent = "Please enter valid measurements.";
return;
}
var bodyFatPercentage = 0;
var logHeight = Math.log(height) / Math.log(10); // Base-10 logarithm for height
if (gender === "male") {
// Hide hip input for males
document.getElementById("hipGroup").style.display = "none";
if (isNaN(hipCircumference)) hipCircumference = 0; // Ensure it's a number, though not used
var logWaistNeck = Math.log(waistCircumference – neckCircumference) / Math.log(10); // Base-10 logarithm for (Waist – Neck)
if (waistCircumference <= neckCircumference) {
resultValueDiv.textContent = "Error";
resultLabelDiv.textContent = "Waist must be larger than Neck for men.";
return;
}
bodyFatPercentage = 495 / (1.0324 – (0.19077 * logWaistNeck) + (0.15456 * logHeight)) – 450;
} else if (gender === "female") {
// Show hip input for females
document.getElementById("hipGroup").style.display = "flex";
if (isNaN(hipCircumference) || hipCircumference <= 0) {
resultValueDiv.textContent = "Error";
resultLabelDiv.textContent = "Please enter Hip Circumference for women.";
return;
}
var logWaistHipNeck = Math.log(waistCircumference + hipCircumference – neckCircumference) / Math.log(10); // Base-10 logarithm for (Waist + Hip – Neck)
if (waistCircumference + hipCircumference <= neckCircumference) {
resultValueDiv.textContent = "Error";
resultLabelDiv.textContent = "Waist + Hip must be larger than Neck for women.";
return;
}
bodyFatPercentage = 495 / (1.29579 – (0.35004 * logWaistHipNeck) + (0.22100 * logHeight)) – 450;
}
// Ensure the result is not a negative number (can happen with extreme measurements)
if (bodyFatPercentage 100) {
bodyFatPercentage = 100;
}
resultValueDiv.textContent = bodyFatPercentage.toFixed(1) + "%";
resultLabelDiv.textContent = "Estimated Body Fat Percentage";
}
// Initialize gender-specific input visibility on load
document.addEventListener('DOMContentLoaded', function() {
var genderSelect = document.getElementById('gender');
var hipGroup = document.getElementById('hipGroup');
function toggleHipInput() {
if (genderSelect.value === 'female') {
hipGroup.style.display = 'flex';
} else {
hipGroup.style.display = 'none';
}
}
toggleHipInput(); // Set initial state
genderSelect.addEventListener('change', toggleHipInput);
});