Athlete Body Fat Percentage Calculator
ANA›Life Services Authority›National Calculator Authority›Athlete Body Fat Percentage Calculator
.calc-container { max-width: 640px; margin: 2rem 0; padding: 1.5rem; background: #fff; border: 1px solid #ddd; border-radius: 8px; box-shadow: 0 1px 3px rgba(0,0,0,0.06); font-family: system-ui, -apple-system, sans-serif; } .calc-container h3 { font-family: Georgia, serif; font-size: 1.15rem; color: #1a1a1a; margin-bottom: 1rem; padding-bottom: 0.5rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-row { display: flex; align-items: center; gap: 0.75rem; margin-bottom: 0.75rem; flex-wrap: wrap; } .calc-row label { min-width: 160px; font-size: 0.9rem; color: #333; font-weight: 500; } .calc-row input[type="number"], .calc-row select { flex: 1; min-width: 120px; max-width: 200px; padding: 0.5rem 0.6rem; border: 1px solid #ccc; border-radius: 4px; font-size: 0.9rem; font-family: system-ui, sans-serif; color: #1a1a1a; background: #fafaf8; } .calc-row input:focus, .calc-row select:focus { outline: none; border-color: var(--ac, #3d5a80); box-shadow: 0 0 0 2px rgba(26,74,138,0.12); } .calc-row .unit { font-size: 0.82rem; color: #888; min-width: 30px; } .calc-btn { display: inline-block; margin-top: 0.5rem; padding: 0.55rem 1.5rem; background: var(--ac, #3d5a80); color: #fff; border: none; border-radius: 4px; font-size: 0.9rem; font-weight: 600; cursor: pointer; font-family: system-ui, sans-serif; } .calc-btn:hover { opacity: 0.9; } .calc-result { margin-top: 1.25rem; padding: 1rem 1.25rem; background: #f0f6fc; border-left: 3px solid var(--ac, #3d5a80); border-radius: 0 6px 6px 0; display: none; } .calc-result.visible { display: block; } .calc-result-label { font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.06em; color: #666; margin-bottom: 0.25rem; } .calc-result-value { font-size: 1.6rem; font-weight: 700; color: var(--ac, #3d5a80); } .calc-result-detail { font-size: 0.85rem; color: #555; margin-top: 0.5rem; line-height: 1.5; } .calc-note { margin-top: 1rem; font-size: 0.8rem; color: #888; font-style: italic; } .calc-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 0.75rem; margin-top: 0.75rem; } .calc-grid-item { padding: 0.6rem 0.8rem; background: #f8f9fa; border-radius: 4px; border: 1px solid #eee; } .calc-grid-item .label { font-size: 0.75rem; color: #888; text-transform: uppercase; letter-spacing: 0.04em; } .calc-grid-item .value { font-size: 1.1rem; font-weight: 600; color: #1a1a1a; } @media (max-width: 720px) { .calc-row { flex-direction: column; align-items: flex-start; gap: 0.3rem; } .calc-row label { min-width: auto; } .calc-row input[type="number"], .calc-row select { max-width: 100%; width: 100%; } .calc-grid { grid-template-columns: 1fr; } } .calc-chart { margin: 1rem 0; text-align: center; } .calc-chart svg { max-width: 100%; height: auto; } .calc-chart-legend { display: flex; flex-wrap: wrap; justify-content: center; gap: 0.6rem 1.2rem; margin-top: 0.6rem; font-size: 0.8rem; color: #555; } .calc-chart-legend span { display: inline-flex; align-items: center; gap: 0.3rem; } .calc-chart-legend i { display: inline-block; width: 10px; height: 10px; border-radius: 2px; font-style: normal; } .calc-related { max-width: 640px; margin: 2rem 0 1rem; padding: 1.25rem 1.5rem; background: #f8f9fa; border: 1px solid #e8e8e8; border-radius: 8px; } .calc-related h3 { font-family: Georgia, serif; font-size: 1rem; color: #1a1a1a; margin: 0 0 0.75rem; padding-bottom: 0.4rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-related-list { list-style: none; padding: 0; margin: 0 0 0.75rem; display: grid; grid-template-columns: 1fr 1fr; gap: 0.4rem 1.5rem; } .calc-related-list li a { font-size: 0.88rem; color: var(--ac, #3d5a80); text-decoration: none; } .calc-related-list li a:hover { text-decoration: underline; } .calc-browse-all { margin: 0.5rem 0 0; font-size: 0.9rem; font-weight: 600; } .calc-browse-all a { color: var(--ac, #3d5a80); text-decoration: none; } .calc-browse-all a:hover { text-decoration: underline; } @media (max-width: 720px) { .calc-related-list { grid-template-columns: 1fr; } }
Athlete Body Fat Percentage Calculator
Estimate your body fat percentage using the U.S. Navy circumference method — widely used for athletes and fitness assessments.
Sex
Male Female
Unit System
Imperial (in, lb) Metric (cm, kg)
Height (in)
Weight (lb)
Neck Circumference (in)
Waist Circumference (in)
Hip Circumference (in)
Age (years)
Calculate
function athToggleFields() { var gender = document.getElementById('ath-gender').value; document.getElementById('ath-hip-field').style.display = (gender === 'female') ? 'flex' : 'none'; }
function athToggleUnits() { var unit = document.getElementById('ath-unit').value; var isMetric = (unit === 'metric'); document.getElementById('ath-height-label').textContent = isMetric ? 'Height (cm)' : 'Height (in)'; document.getElementById('ath-weight-label').textContent = isMetric ? 'Weight (kg)' : 'Weight (lb)'; document.getElementById('ath-neck-label').textContent = isMetric ? 'Neck Circumference (cm)' : 'Neck Circumference (in)'; document.getElementById('ath-waist-label').textContent = isMetric ? 'Waist Circumference (cm)' : 'Waist Circumference (in)'; document.getElementById('ath-hip-label').textContent = isMetric ? 'Hip Circumference (cm)' : 'Hip Circumference (in)'; // Reset placeholders if (isMetric) { document.getElementById('ath-height').placeholder = 'e.g. 178'; document.getElementById('ath-weight').placeholder = 'e.g. 82'; document.getElementById('ath-neck').placeholder = 'e.g. 38'; document.getElementById('ath-waist').placeholder = 'e.g. 81'; document.getElementById('ath-hip').placeholder = 'e.g. 97'; } else { document.getElementById('ath-height').placeholder = 'e.g. 70'; document.getElementById('ath-weight').placeholder = 'e.g. 180'; document.getElementById('ath-neck').placeholder = 'e.g. 15'; document.getElementById('ath-waist').placeholder = 'e.g. 32'; document.getElementById('ath-hip').placeholder = 'e.g. 38'; } }
function athCalc() { var resultDiv = document.getElementById('ath-result'); resultDiv.style.display = 'block'; resultDiv.className = 'calc-result';
var gender = document.getElementById('ath-gender').value; var unit = document.getElementById('ath-unit').value;
var height = parseFloat(document.getElementById('ath-height').value); var weight = parseFloat(document.getElementById('ath-weight').value); var neck = parseFloat(document.getElementById('ath-neck').value); var waist = parseFloat(document.getElementById('ath-waist').value); var age = parseFloat(document.getElementById('ath-age').value); var hip = (gender === 'female') ? parseFloat(document.getElementById('ath-hip').value) : 0;
// Validation if (isNaN(height) || height ⚠ Please enter a valid height.'; return; } if (isNaN(weight) || weight ⚠ Please enter a valid weight.'; return; } if (isNaN(neck) || neck ⚠ Please enter a valid neck circumference.'; return; } if (isNaN(waist) || waist ⚠ Please enter a valid waist circumference.'; return; } if (gender === 'female' && (isNaN(hip) || hip ⚠ Please enter a valid hip circumference.'; return; } if (isNaN(age) || age 100) { resultDiv.innerHTML = '⚠ Please enter a valid age (10–100).'; return; }
// Convert metric → imperial for formula (formula uses inches) var hIn, nIn, wIn, hipIn; if (unit === 'metric') { hIn = height / 2.54; nIn = neck / 2.54; wIn = waist / 2.54; hipIn = hip / 2.54; weight = weight * 2.20462; // kg → lb (for BMI-based lean mass) } else { hIn = height; nIn = neck; wIn = waist; hipIn = hip; }
// Validation: waist must be > neck if (wIn ⚠ Waist circumference must be greater than neck circumference.'; return; } if (gender === 'female' && (wIn + hipIn) ⚠ (Waist + Hip) must be greater than neck circumference.'; return; }
// U.S. Navy Body Fat Formula var bf; if (gender === 'male') { // BF% = 86.010 × log10(waist − neck) − 70.041 × log10(height) + 36.76 var logArg1 = Math.log10(wIn - nIn); var logArg2 = Math.log10(hIn); bf = 86.010 * logArg1 - 70.041 * logArg2 + 36.76; } else { // BF% = 163.205 × log10(waist + hip − neck) − 97.684 × log10(height) − 78.387 var logArg1 = Math.log10(wIn + hipIn - nIn); var logArg2 = Math.log10(hIn); bf = 163.205 * logArg1 - 97.684 * logArg2 - 78.387; }
if (isNaN(bf) || !isFinite(bf)) { resultDiv.innerHTML = '⚠ Could not compute body fat. Please check your measurements.'; return; }
bf = Math.max(2, Math.min(bf, 70)); // clamp to physiological range
// Fat mass & lean mass var weightLb = weight; // already in lb var fatMassLb = (bf / 100) * weightLb; var leanMassLb = weightLb - fatMassLb; var fatMassKg = fatMassLb / 2.20462; var leanMassKg = leanMassLb / 2.20462;
// Category var category, catColor; if (gender === 'male') { if (bf ' + 'Body Fat Percentage' + '' + bf.toFixed(1) + '%' + 'Category' + '' + category + '' + 'Fat Mass' + '' + fatMassDisplay + ' ' + massUnit + '' + 'Lean Mass' + '' + leanMassDisplay + ' ' + massUnit + '' + 'Athlete Ideal Range' + '' + idealLow + '% – ' + idealHigh + '%' + '' + 'Measured at the navel (waist) and widest point (hip). Results are estimates; consult a professional for clinical assessment.
'; }
#### Formula — U.S. Navy Circumference Method
Male: BF% = 86.010 × log₁₀(waist − neck) − 70.041 × log₁₀(height) + 36.76
Female: BF% = 163.205 × log₁₀(waist + hip − neck) − 97.684 × log₁₀(height) − 78.387
All measurements in inches. Developed by Hodgdon & Beckett (1984) for the U.S. Navy.
Fat Mass = BF% × Total Weight Lean Mass = Total Weight − Fat Mass
#### Assumptions & References
- Based on the U.S. Navy circumference method (Hodgdon & Beckett, 1984), validated for athletic populations.
- Waist is measured at the navel level; hip at the widest point (females only); neck just below the larynx.
- Reference: Hodgdon, J.A. & Beckett, M.B. (1984). Prediction of percent body fat for U.S. Navy men and women. Naval Health Research Center.
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