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| 1 | +{ |
| 2 | + "title": "Body Fat Calculator (US Navy Method)", |
| 3 | + "shortDescription": "Estimate body fat percentage using the US Navy method (waist, neck, and hip for women). Returns fat mass, lean mass, and fitness category.", |
| 4 | + "description": "Enter your height, weight, neck, waist (and hip for women) circumferences. The US Navy formula gives a body fat percentage that's reasonably accurate without expensive scans, plus your fat-free lean mass.", |
| 5 | + "metaDescription": "Free body fat calculator using US Navy circumference method. Just need a tape measure. Shows body fat %, fat mass, lean mass, and fitness category.", |
| 6 | + "keywords": ["body fat calculator", "US Navy body fat", "body fat percentage", "fat mass calculator", "lean body mass"], |
| 7 | + "empty": "Enter your measurements to estimate body fat.", |
| 8 | + "sex": { "male": "Male", "female": "Female" }, |
| 9 | + "input": { |
| 10 | + "height": "Height", |
| 11 | + "weight": "Weight", |
| 12 | + "waist": "Waist", |
| 13 | + "neck": "Neck", |
| 14 | + "hip": "Hip" |
| 15 | + }, |
| 16 | + "result": { |
| 17 | + "fatMass": "Fat mass", |
| 18 | + "leanMass": "Lean mass" |
| 19 | + }, |
| 20 | + "category": { |
| 21 | + "essential": "Essential fat", |
| 22 | + "athlete": "Athlete", |
| 23 | + "fit": "Fitness", |
| 24 | + "average": "Average", |
| 25 | + "obese": "Obese" |
| 26 | + }, |
| 27 | + "article": { |
| 28 | + "sections": [ |
| 29 | + { |
| 30 | + "heading": "How the US Navy method works", |
| 31 | + "paragraphs": [ |
| 32 | + "The US Navy circumference method estimates body fat using the relationship between waist, neck (and hip, for women) measurements relative to height. The formulas were developed by Hodgdon and Beckett in 1984 and remain the standard for military body composition assessment because they require only a tape measure and produce results within ±3-4% of more expensive methods like DEXA scans for the average adult.", |
| 33 | + "Men: %BF = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76. Women: %BF = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387. Measurements are in centimeters." |
| 34 | + ] |
| 35 | + }, |
| 36 | + { |
| 37 | + "heading": "Body fat ranges and what they mean", |
| 38 | + "paragraphs": [ |
| 39 | + "Essential fat (men 2-5%, women 10-13%): the absolute minimum your body needs for vital functions. Below this is dangerous and impossible to maintain.", |
| 40 | + "Athlete (men 6-13%, women 14-20%): visible muscle definition, low fat. Common in competitive endurance athletes and physique competitors.", |
| 41 | + "Fitness (men 14-17%, women 21-24%): healthy and athletic-looking. Most regular exercisers fall here. This is typically the maintenance target for active adults.", |
| 42 | + "Average (men 18-24%, women 25-31%): the median for the general adult population. Not unhealthy in itself but raises some risk factors at the upper end.", |
| 43 | + "Obese (men 25%+, women 32%+): elevated risk of cardiovascular disease, diabetes, and other conditions. Targeting reduction to fitness range improves long-term health outcomes." |
| 44 | + ] |
| 45 | + }, |
| 46 | + { |
| 47 | + "heading": "Accuracy and limitations", |
| 48 | + "paragraphs": [ |
| 49 | + "The US Navy method is good for tracking changes over time in the same person. Less reliable for absolute accuracy: very muscular individuals tend to be overestimated, and individuals with abnormally large or small frames (very narrow shoulders, very wide hips) may also see error.", |
| 50 | + "For the most accurate measurement, DEXA (dual-energy X-ray absorptiometry) is the clinical gold standard. BodPod and underwater weighing are also highly accurate. Bioelectrical impedance scales are convenient but vary by 3-8% from day to day depending on hydration. Skin calipers, when used by a trained person, are nearly as accurate as the Navy method.", |
| 51 | + "Measurement consistency matters more than absolute accuracy when tracking progress. Take measurements first thing in the morning, after using the bathroom, before eating or drinking, and use the same tape measure tension. Variation of 1-2 cm at the waist can shift the result by 1%." |
| 52 | + ] |
| 53 | + } |
| 54 | + ], |
| 55 | + "howTo": [ |
| 56 | + { "name": "Pick your sex", "text": "Female version uses an additional hip measurement." }, |
| 57 | + { "name": "Measure height and weight", "text": "Standard measurements." }, |
| 58 | + { "name": "Measure waist", "text": "At the navel, with a relaxed abdomen, tape parallel to the floor." }, |
| 59 | + { "name": "Measure neck", "text": "Just below the larynx (Adam's apple), tape sloping slightly downward at the front." }, |
| 60 | + { "name": "Measure hip (women)", "text": "At the widest point, tape level with the floor." }, |
| 61 | + { "name": "Read your body fat percentage", "text": "Plus fat mass, lean mass, and fitness category." } |
| 62 | + ] |
| 63 | + }, |
| 64 | + "faq": [ |
| 65 | + { "q": "How accurate is the US Navy method?", "a": "Within ±3-4% of clinical methods (DEXA) for typical adults. Less accurate for very muscular or atypically-shaped bodies." }, |
| 66 | + { "q": "Is body fat better than BMI?", "a": "For health assessment, generally yes — BMI doesn't distinguish muscle from fat. A bodybuilder may have BMI 30 (obese) and body fat 8% (athlete). Body fat is more meaningful." }, |
| 67 | + { "q": "What's a healthy body fat percentage?", "a": "Men: 14-24% (fitness-to-average range). Women: 21-31%. Below 5% (men) or 13% (women) is dangerous; above 25% (men) or 32% (women) raises health risks." }, |
| 68 | + { "q": "Why do I need to measure my neck?", "a": "Neck circumference correlates with overall lean mass and acts as a 'reference' to calibrate the formula. Skipping it would lose accuracy." }, |
| 69 | + { "q": "How often should I measure?", "a": "Weekly is usually enough for tracking weight loss or muscle gain progress. Daily measurements bounce too much from hydration and meal timing to be useful." }, |
| 70 | + { "q": "Should I measure before or after exercise?", "a": "Before, ideally first thing in the morning after using the bathroom. Post-exercise measurements are skewed by sweat loss and tissue swelling." }, |
| 71 | + { "q": "Why is the female formula different?", "a": "Women carry more body fat in hip and thigh regions on average, so adding hip circumference improves accuracy. The constants differ to reflect typical female body composition." }, |
| 72 | + { "q": "Does the data leave my browser?", "a": "No. Calculation is local; nothing is sent to a server." } |
| 73 | + ] |
| 74 | +} |
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