Percentage Body Fat Calculator

Percentage Body Fat Calculator

Use this calculator to estimate your body fat percentage based on the U.S. Navy Body Fat Measurement Method. This method uses circumference measurements of your body to provide an estimate. All measurements should be in inches.

	Male Female

function toggleHipInput() { var gender = document.getElementById('gender').value; var hipRow = document.getElementById('hipRow'); if (gender === 'female') { hipRow.style.display = 'table-row'; } else { hipRow.style.display = 'none'; } } function calculateBodyFat() { var gender = document.getElementById('gender').value; var height = parseFloat(document.getElementById('height').value); var neck = parseFloat(document.getElementById('neckCircumference').value); var waist = parseFloat(document.getElementById('waistCircumference').value); var hip = parseFloat(document.getElementById('hipCircumference').value); var resultDiv = document.getElementById('result'); var bodyFatPercentage; // Input validation if (isNaN(height) || height <= 0 || isNaN(neck) || neck <= 0 || isNaN(waist) || waist <= 0) { resultDiv.style.display = 'block'; resultDiv.style.backgroundColor = '#f8d7da'; resultDiv.style.borderColor = '#f5c6cb'; resultDiv.style.color = '#721c24'; resultDiv.innerHTML = 'Please enter valid positive numbers for all required fields.'; return; } if (gender === 'male') { if (waist <= neck) { resultDiv.style.display = 'block'; resultDiv.style.backgroundColor = '#f8d7da'; resultDiv.style.borderColor = '#f5c6cb'; resultDiv.style.color = '#721c24'; resultDiv.innerHTML = 'For men, waist circumference must be greater than neck circumference.'; return; } var log10_waist_neck = Math.log10(waist – neck); var log10_height = Math.log10(height); var bodyDensity = 1.0324 – 0.19077 * log10_waist_neck + 0.15456 * log10_height; bodyFatPercentage = (495 / bodyDensity) – 450; } else { // female if (isNaN(hip) || hip <= 0) { resultDiv.style.display = 'block'; resultDiv.style.backgroundColor = '#f8d7da'; resultDiv.style.borderColor = '#f5c6cb'; resultDiv.style.color = '#721c24'; resultDiv.innerHTML = 'Please enter a valid positive number for Hip Circumference.'; return; } if ((waist + hip) <= neck) { resultDiv.style.display = 'block'; resultDiv.style.backgroundColor = '#f8d7da'; resultDiv.style.borderColor = '#f5c6cb'; resultDiv.style.color = '#721c24'; resultDiv.innerHTML = 'For women, (waist + hip) circumference must be greater than neck circumference.'; return; } var log10_waist_hip_neck = Math.log10(waist + hip – neck); var log10_height = Math.log10(height); var bodyDensity = 1.29579 – 0.35004 * log10_waist_hip_neck + 0.22100 * log10_height; bodyFatPercentage = (495 / bodyDensity) – 450; } if (isNaN(bodyFatPercentage) || !isFinite(bodyFatPercentage) || bodyFatPercentage < 0) { resultDiv.style.display = 'block'; resultDiv.style.backgroundColor = '#f8d7da'; resultDiv.style.borderColor = '#f5c6cb'; resultDiv.style.color = '#721c24'; resultDiv.innerHTML = 'Could not calculate body fat percentage. Please check your measurements.'; } else { resultDiv.style.display = 'block'; resultDiv.style.backgroundColor = '#e9f7ef'; resultDiv.style.borderColor = '#d4edda'; resultDiv.style.color = '#155724'; resultDiv.innerHTML = 'Your estimated Body Fat Percentage: ' + bodyFatPercentage.toFixed(2) + '%'; } } // Initialize hip input visibility on page load window.onload = toggleHipInput;

Understanding Body Fat Percentage

Body fat percentage is a measure of how much of your total body weight is made up of fat. It's often considered a more accurate indicator of health and fitness than Body Mass Index (BMI), as BMI doesn't differentiate between fat and muscle mass. A person with a high muscle mass might have a high BMI but a healthy body fat percentage, while someone with a low muscle mass could have a normal BMI but an unhealthy body fat percentage.

Why is Body Fat Percentage Important?

• Health Risk Assessment: Both excessively low and excessively high body fat percentages can pose health risks. High body fat is associated with conditions like heart disease, type 2 diabetes, high blood pressure, and certain cancers.
• Fitness Goals: Athletes and fitness enthusiasts often monitor body fat percentage to track progress, optimize performance, and achieve specific aesthetic goals.
• Body Composition Insight: It provides a clearer picture of your body composition, helping you understand if changes in weight are due to fat loss/gain or muscle loss/gain.

How is Body Fat Measured?

There are several methods to measure body fat, each with varying levels of accuracy and cost:

• DEXA Scan (Dual-energy X-ray Absorptiometry): Considered one of the most accurate methods, it uses X-rays to differentiate between bone, lean mass, and fat.
• Hydrostatic Weighing (Underwater Weighing): Measures body density by submerging a person in water. Highly accurate but requires specialized equipment.
• Bioelectrical Impedance Analysis (BIA): Uses a small electrical current to estimate body fat. Accuracy can vary based on hydration levels and device quality.
• Skinfold Calipers: Measures the thickness of skinfolds at various sites on the body. Requires skill and experience for accurate results.
• Circumference Measurements (U.S. Navy Method): This is the method used in our calculator. It's a practical and accessible way to estimate body fat using a tape measure. While not as precise as DEXA, it provides a reasonable estimate for tracking changes over time.

Healthy Body Fat Ranges

Healthy body fat percentages vary by age and gender. The American Council on Exercise (ACE) provides general guidelines:

Category	Women (% Fat)	Men (% Fat)
Essential Fat	10-13%	2-5%
Athletes	14-20%	6-13%
Fitness	21-24%	14-17%
Acceptable	25-31%	18-24%
Obese	32%+	25%+

Source: American Council on Exercise (ACE)

How to Take Measurements for the U.S. Navy Method:

• Height: Stand tall without shoes, measure from the top of your head to the floor.
• Neck: Measure horizontally around the neck, just below the larynx (Adam's apple). Keep the tape parallel to the floor.
• Waist (Men): Measure horizontally around the abdomen at the navel (belly button). Do not suck in your stomach.
• Waist (Women): Measure horizontally around the narrowest part of the abdomen, usually just above the navel.
• Hip (Women only): Measure horizontally around the largest circumference of the buttocks.

Ensure the tape measure is snug but not compressing the skin. Take measurements multiple times and use the average for better accuracy.

Examples of Body Fat Calculation

Let's look at a couple of examples using the U.S. Navy Body Fat Measurement Method.

Example 1: Male

• Gender: Male
• Height: 70 inches
• Neck Circumference: 16 inches
• Waist Circumference: 34 inches

Using the formula for men:
Body Density = 1.0324 - 0.19077 * log10(34 - 16) + 0.15456 * log10(70)
Body Density = 1.0324 - 0.19077 * log10(18) + 0.15456 * log10(70)
Body Density = 1.0324 - 0.19077 * 1.25527 + 0.15456 * 1.84510
Body Density = 1.0324 - 0.23949 + 0.28527 = 1.07818
Body Fat % = (495 / 1.07818) - 450 = 459.10 - 450 = 9.10%

This individual's estimated body fat percentage is approximately 9.10%, which falls into the "Athletes" category for men.

Example 2: Female

• Gender: Female
• Height: 65 inches
• Neck Circumference: 13 inches
• Waist Circumference: 28 inches
• Hip Circumference: 38 inches

Using the formula for women:
Body Density = 1.29579 - 0.35004 * log10(28 + 38 - 13) + 0.22100 * log10(65)
Body Density = 1.29579 - 0.35004 * log10(53) + 0.22100 * log10(65)
Body Density = 1.29579 - 0.35004 * 1.72428 + 0.22100 * 1.81291
Body Density = 1.29579 - 0.60350 + 0.40065 = 1.09294
Body Fat % = (495 / 1.09294) - 450 = 452.99 - 450 = 2.99%

This individual's estimated body fat percentage is approximately 2.99%. This is very low, falling into the "Essential Fat" category, which might indicate a need to increase body fat for optimal health.

Disclaimer

This calculator provides an estimate based on the U.S. Navy Body Fat Measurement Method, which is a circumference-based calculation. While convenient, it is not as accurate as clinical methods like DEXA scans or hydrostatic weighing. Factors such as individual body shape, measurement technique, and hydration levels can influence the results. Always consult with a healthcare professional or certified fitness expert for personalized advice and accurate body composition analysis.