Calculate your body fat percentage using the U.S. Navy Method
Enter Your Measurements
Your Results
Body Fat Percentage:0%
Body Fat Mass:0 lbs
Lean Body Mass:0 lbs
Category:–
Body Mass Index (BMI):0
Understanding Body Fat Percentage
Body fat percentage is the proportion of fat in your body compared to your total body weight. Unlike BMI, which only considers height and weight, body fat percentage provides a more accurate picture of your body composition and overall health.
Why Body Fat Percentage Matters
Knowing your body fat percentage helps you understand your fitness level, health risks, and whether your weight loss or muscle gain goals are on track. It's a more reliable indicator of health than weight alone.
The U.S. Navy Method
This calculator uses the U.S. Navy circumference method, which estimates body fat percentage based on measurements of your neck, waist, height, and (for women) hips. The formulas are:
Body Fat % = 163.205 × log10(waist + hip – neck) – 97.684 × log10(height) – 78.387
Body Fat Categories
Essential Fat
Men: 2-5% | Women: 10-13%
Minimum required for basic physiological functions
Athletes
Men: 6-13% | Women: 14-20%
Typical range for competitive athletes
Fitness
Men: 14-17% | Women: 21-24%
Fit and healthy appearance
Average
Men: 18-24% | Women: 25-31%
Typical for general population
How to Take Accurate Measurements
Neck: Measure just below the larynx (Adam's apple) with the tape measure perpendicular to the long axis of the neck
Waist (Men): Measure horizontally at the level of the navel
Waist (Women): Measure at the narrowest point, typically just above the navel
Hips (Women only): Measure at the largest horizontal circumference around the hips and buttocks
Height: Measure without shoes, standing straight against a wall
Factors Affecting Body Fat Percentage
Several factors influence your body fat percentage:
Age: Body fat tends to increase with age as metabolism slows and muscle mass decreases
Gender: Women naturally have higher body fat percentages due to biological differences
Genetics: Your genetic makeup affects how and where your body stores fat
Activity Level: Regular exercise, especially resistance training, helps maintain lower body fat
Diet: Caloric intake and nutritional quality directly impact body composition
Hormones: Hormonal imbalances can affect fat distribution and storage
Healthy Body Fat Ranges
Maintaining a healthy body fat percentage is crucial for optimal health and performance:
Men:
Essential: 2-5%
Athletes: 6-13%
Fitness: 14-17%
Average: 18-24%
Obese: 25%+
Women:
Essential: 10-13%
Athletes: 14-20%
Fitness: 21-24%
Average: 25-31%
Obese: 32%+
Tips for Reducing Body Fat
Create a Caloric Deficit: Consume fewer calories than you burn, but don't go below 1200-1500 calories per day
Strength Training: Build muscle to increase metabolism and burn more calories at rest
Cardiovascular Exercise: Include 150-300 minutes of moderate-intensity cardio per week
Protein Intake: Consume 0.8-1.2 grams of protein per pound of body weight to preserve muscle
Sleep Quality: Aim for 7-9 hours of quality sleep to optimize hormone balance
Stress Management: High cortisol from chronic stress can promote fat storage
Consistency: Sustainable changes over time are more effective than extreme diets
Limitations of the Navy Method
While the U.S. Navy method is convenient and reasonably accurate, it has some limitations:
Accuracy can vary by ±3-4% compared to more precise methods like DEXA scans
Results may be less accurate for very muscular or very obese individuals
Measurement errors can significantly impact results
Does not account for visceral fat distribution
Alternative Measurement Methods
Other methods for measuring body fat include:
DEXA Scan: Most accurate, uses X-rays to measure bone, muscle, and fat
Hydrostatic Weighing: Underwater weighing based on body density
Bod Pod: Air displacement plethysmography
Skinfold Calipers: Measures subcutaneous fat at specific body sites
Bioelectrical Impedance: Sends electrical signals through the body (less accurate)
Important Note
This calculator provides estimates based on the U.S. Navy circumference method. For the most accurate assessment, consult with a healthcare professional or use clinical-grade body composition analysis methods. Always consult your doctor before starting any diet or exercise program.
function toggleGenderFields() {
var gender = document.querySelector('input[name="gender"]:checked').value;
var hipGroup = document.getElementById('hipGroup');
if (gender === 'female') {
hipGroup.style.display = 'block';
} else {
hipGroup.style.display = 'none';
}
}
function calculateBodyFat() {
var gender = document.querySelector('input[name="gender"]:checked').value;
var age = parseFloat(document.getElementById('age').value);
var height = parseFloat(document.getElementById('height').value);
var weight = parseFloat(document.getElementById('weight').value);
var neck = parseFloat(document.getElementById('neck').value);
var waist = parseFloat(document.getElementById('waist').value);
var hip = parseFloat(document.getElementById('hip').value);
if (isNaN(age) || isNaN(height) || isNaN(weight) || isNaN(neck) || isNaN(waist)) {
alert('Please enter valid numbers for all required fields.');
return;
}
if (gender === 'female' && isNaN(hip)) {
alert('Please enter your hip measurement.');
return;
}
if (age 100) {
alert('Please enter a valid age between 18 and 100.');
return;
}
if (height 96) {
alert('Please enter a valid height between 48 and 96 inches.');
return;
}
if (weight 500) {
alert('Please enter a valid weight between 80 and 500 pounds.');
return;
}
var bodyFatPercentage;
if (gender === 'male') {
bodyFatPercentage = 86.010 * Math.log10(waist – neck) – 70.041 * Math.log10(height) + 36.76;
} else {
bodyFatPercentage = 163.205 * Math.log10(waist + hip – neck) – 97.684 * Math.log10(height) – 78.387;
}
if (isNaN(bodyFatPercentage) || bodyFatPercentage = 2 && bodyFatPercentage = 6 && bodyFatPercentage = 14 && bodyFatPercentage = 18 && bodyFatPercentage = 25) {
category = 'Obese';
categoryClass = 'obese';
} else {
category = 'Below Essential';
categoryClass = 'essential';
}
} else {
if (bodyFatPercentage >= 10 && bodyFatPercentage = 14 && bodyFatPercentage = 21 && bodyFatPercentage = 25 && bodyFatPercentage = 32) {
category = 'Obese';
categoryClass = 'obese';
} else {
category = 'Below Essential';
categoryClass = 'essential';
}
}
document.getElementById('bodyFatPercent').textContent = bodyFatPercentage.toFixed(1) + '%';
document.getElementById('fatMass').textContent = fatMass.toFixed(1) + ' lbs';
document.getElementById('leanMass').textContent = leanMass.toFixed(1) + ' lbs';
document.getElementById('bmi').textContent = bmi.toFixed(1);
var categoryElement = document.getElementById('category');
categoryElement.textContent = category;
categoryElement.className = 'category ' + categoryClass;
var resultDiv = document.getElementById('result');
resultDiv.classList.add('show');
}
window.onload = function() {
toggleGenderFields();
};