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Navy Method Body Fat Calculator

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function calculateBodyFat() { var gender = document.querySelector('input[name="gender"]:checked').value; var height = parseFloat(document.getElementById('height').value); var neck = parseFloat(document.getElementById('neck').value); var waist = parseFloat(document.getElementById('waist').value); var hips = parseFloat(document.getElementById('hips').value); var resultContainer = document.getElementById('result-container'); var bfValueDisplay = document.getElementById('bf-value'); var bfCategoryDisplay = document.getElementById('bf-category'); if (!height || !neck || !waist || (gender === 'female' && !hips)) { alert('Please fill in all fields with valid numbers.'); return; } var bodyFat = 0; if (gender === 'male') { // US Navy Formula for Men (Metric) // BF% = 495 / (1.0324 – 0.19077 * log10(waist – neck) + 0.15456 * log10(height)) – 450 bodyFat = 495 / (1.0324 – 0.19077 * Math.log10(waist – neck) + 0.15456 * Math.log10(height)) – 450; } else { // US Navy Formula for Women (Metric) // BF% = 495 / (1.29579 – 0.35004 * log10(waist + hip – neck) + 0.22100 * log10(height)) – 450 bodyFat = 495 / (1.29579 – 0.35004 * Math.log10(waist + hips – neck) + 0.22100 * Math.log10(height)) – 450; } if (isNaN(bodyFat) || bodyFat < 0) { alert('Calculation error. Please ensure your measurements are realistic.'); return; } var category = ""; if (gender === 'male') { if (bodyFat < 6) category = "Essential Fat"; else if (bodyFat < 14) category = "Athletes"; else if (bodyFat < 18) category = "Fitness"; else if (bodyFat < 25) category = "Average"; else category = "Obese"; } else { if (bodyFat < 14) category = "Essential Fat"; else if (bodyFat < 21) category = "Athletes"; else if (bodyFat < 25) category = "Fitness"; else if (bodyFat < 32) category = "Average"; else category = "Obese"; } bfValueDisplay.innerHTML = bodyFat.toFixed(1) + "%"; bfCategoryDisplay.innerHTML = "Category: " + category; resultContainer.style.display = 'block'; resultContainer.scrollIntoView({ behavior: 'smooth' }); }

Understanding the Navy Method Body Fat Calculator

Body fat percentage is a much more accurate indicator of health and fitness levels than BMI (Body Mass Index). While BMI only considers your weight and height, the Navy Method Body Fat Calculator uses specific circumference measurements to estimate lean mass and adipose tissue.

Developed by the U.S. Navy in the late 1980s, this method was designed to provide a reliable estimate of body composition without the need for expensive equipment like DEXA scans or hydrostatic weighing. It is widely considered one of the most accurate "tape measure" methods available.

How to Take Accurate Measurements

To get the most accurate result from our calculator, follow these measurement protocols:

• Height: Measure without shoes, standing straight against a wall.
• Neck: Measure just below the larynx (Adam's apple), with the tape sloping slightly downward toward the front. Avoid tensing your neck muscles.
• Waist (Men): Measure at the navel level (belly button). Do not suck in your stomach.
• Waist (Women): Measure at the narrowest point of the natural waistline (usually halfway between the ribs and the navel).
• Hips (Women only): Measure at the widest point of the buttocks/hips.

Body Fat Categories Table

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

Calculation Examples

Example 1: Male Athlete
Height: 180cm, Neck: 40cm, Waist: 85cm.
Result: Approximately 15.2% (Fitness Category).

Example 2: Female Fitness Enthusiast
Height: 165cm, Neck: 34cm, Waist: 70cm, Hips: 92cm.
Result: Approximately 22.4% (Fitness Category).

Why Accuracy Varies

While the Navy Method is accurate to within 3-4% for most people, it can over- or under-estimate body fat for certain body types. Bodybuilders with thick necks and narrow waists might receive a lower-than-actual body fat reading, while "skinny fat" individuals might find the results differ from visual assessments. For the best tracking, measure yourself under the same conditions (e.g., morning, fasted) every time.