Use this calculator to estimate your body fat percentage based on the U.S. Army's circumference measurement method (AR 600-9).
Male
Female
function toggleGenderFields() {
var genderMale = document.getElementById('genderMale');
var maleFields = document.getElementById('maleFields');
var femaleFields = document.getElementById('femaleFields');
if (genderMale.checked) {
maleFields.style.display = 'block';
femaleFields.style.display = 'none';
} else {
maleFields.style.display = 'none';
femaleFields.style.display = 'block';
}
}
function calculateBodyFat() {
var height = parseFloat(document.getElementById('heightInches').value);
var neck = parseFloat(document.getElementById('neckCircumference').value);
var genderMale = document.getElementById('genderMale').checked;
var bodyFatPercentage;
var resultDiv = document.getElementById('result');
// Input validation
if (isNaN(height) || height <= 0) {
resultDiv.innerHTML = 'Please enter a valid height.';
return;
}
if (isNaN(neck) || neck <= 0) {
resultDiv.innerHTML = 'Please enter a valid neck circumference.';
return;
}
if (genderMale) {
var abdomen = parseFloat(document.getElementById('abdomenCircumference').value);
if (isNaN(abdomen) || abdomen <= 0) {
resultDiv.innerHTML = 'Please enter a valid abdomen circumference.';
return;
}
var diff = abdomen – neck;
if (diff <= 0) {
resultDiv.innerHTML = 'Abdomen circumference must be greater than neck circumference for a valid male calculation.';
return;
}
// Male Formula: BF% = 86.010 * log10(Abdomen – Neck) – 70.041 * log10(Height) + 36.76
bodyFatPercentage = 86.010 * (Math.log(diff) / Math.LN10) – 70.041 * (Math.log(height) / Math.LN10) + 36.76;
} else {
var waist = parseFloat(document.getElementById('waistCircumference').value);
var hip = parseFloat(document.getElementById('hipCircumference').value);
if (isNaN(waist) || waist <= 0) {
resultDiv.innerHTML = 'Please enter a valid waist circumference.';
return;
}
if (isNaN(hip) || hip <= 0) {
resultDiv.innerHTML = 'Please enter a valid hip circumference.';
return;
}
var sum = waist + hip – neck;
if (sum <= 0) {
resultDiv.innerHTML = 'The sum of waist and hip circumferences must be greater than neck circumference for a valid female calculation.';
return;
}
// Female Formula: BF% = 163.205 * log10(Waist + Hip – Neck) – 97.684 * log10(Height) – 78.387
bodyFatPercentage = 163.205 * (Math.log(sum) / Math.LN10) – 97.684 * (Math.log(height) / Math.LN10) – 78.387;
}
if (isNaN(bodyFatPercentage)) {
resultDiv.innerHTML = 'An error occurred during calculation. Please check your inputs.';
} else {
resultDiv.innerHTML = '
Calculated Body Fat:
Your estimated body fat percentage is: ' + bodyFatPercentage.toFixed(2) + '%';
}
}
// Initialize fields based on default gender selection
document.addEventListener('DOMContentLoaded', toggleGenderFields);
Understanding the Army Body Fat Standards (AR 600-9)
The U.S. Army places significant emphasis on physical fitness and body composition as critical components of soldier readiness. The Army Body Fat Standards, outlined in Army Regulation (AR) 600-9, "The Army Body Composition Program," are designed to ensure that soldiers maintain a healthy weight and body fat percentage conducive to optimal performance and overall health.
Why Body Fat is Measured in the Army
Body composition is a key indicator of a soldier's physical readiness. Excessive body fat can negatively impact physical performance, increase the risk of injuries, and contribute to various health problems. By maintaining appropriate body fat levels, soldiers are better equipped to handle the physical demands of military service, including combat operations, training exercises, and daily duties. The program also aims to promote a healthy lifestyle among service members.
How the Army Measures Body Fat
Unlike some civilian methods that use advanced equipment like DEXA scans or bioelectrical impedance analysis (BIA), the Army primarily uses a simple and consistent circumference-based measurement method. This method involves taking specific measurements of the neck, abdomen (for males), waist, and hips (for females) using a tape measure. These measurements, along with the soldier's height, are then plugged into specific formulas to estimate body fat percentage.
Measurement Points:
Height: Measured to the nearest half-inch.
Neck Circumference: Measured at the point just below the larynx (Adam's apple), perpendicular to the long axis of the neck.
Abdomen Circumference (Males): Measured horizontally at the navel (belly button).
Waist Circumference (Females): Measured horizontally at the narrowest part of the waist, or if no natural waistline, at the level of the navel.
Hip Circumference (Females): Measured horizontally around the largest protrusion of the gluteal muscles (buttocks).
The Formulas Used
The calculator above utilizes the official U.S. Army formulas for estimating body fat percentage:
For Females:Body Fat % = 163.205 * log10(Waist + Hip - Neck) - 97.684 * log10(Height) - 78.387
These formulas are regression equations derived from extensive research to provide a reasonably accurate estimate of body fat based on easily obtainable circumference measurements.
Army Body Fat Standards by Age and Gender
The Army sets maximum allowable body fat percentages that vary by age and gender. Soldiers who exceed these limits are typically enrolled in the Army Body Composition Program (ABCP) and given a period to meet the standards. Failure to meet the standards can have career implications.
Example Maximum Body Fat Percentages (These are general guidelines and subject to change by official Army regulations):
Males:
17-20 years: 20%
21-27 years: 22%
28-39 years: 24%
40+ years: 26%
Females:
17-20 years: 30%
21-27 years: 32%
28-39 years: 34%
40+ years: 36%
It's crucial to consult the most current AR 600-9 for the exact and up-to-date standards.
Important Considerations
Accuracy: While the circumference method is the official Army standard, it is an estimation and may not be as precise as laboratory methods like DEXA. However, its consistency and ease of use make it practical for large-scale military application.
Proper Measurement: The accuracy of the calculation heavily relies on precise and consistent measurements. Small errors in tape placement can lead to significant differences in the calculated percentage.
Not a Diagnostic Tool: This calculator and the Army's method are for body composition assessment within the military context, not for diagnosing medical conditions.
This calculator provides a quick way to estimate your body fat percentage using the Army's method. Remember to always refer to official Army regulations for definitive standards and guidance.