BAC Estimator

ANA›Life Services Authority›National Calculator Authority›BAC Estimator

.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; } }

BAC Estimator

Estimates your Blood Alcohol Content (BAC) using the Widmark formula, adjusted for sex, body weight, number of drinks, and time since drinking began.

Body Weight

lbs kg

Biological Sex

Male Female

Number of Standard Drinks

1 standard drink = 14 g pure alcohol (12 oz beer, 5 oz wine, 1.5 oz spirits)

Hours Since Drinking Began

Calculate BAC

function bacCalc() { var weightRaw = parseFloat(document.getElementById('bac-weight').value); var weightUnit = document.getElementById('bac-weight-unit').value; var sex = document.getElementById('bac-sex').value; var drinks = parseFloat(document.getElementById('bac-drinks').value); var hours = parseFloat(document.getElementById('bac-hours').value); var resultDiv = document.getElementById('bac-result');

// --- Validation --- if (isNaN(weightRaw) || weightRaw Please enter a valid body weight.'; return; } if (isNaN(drinks) || drinks Please enter a valid number of drinks (0 or more).'; return; } if (isNaN(hours) || hours Please enter valid hours since drinking began (0 or more).'; return; }

// Convert weight to grams var weightKg = (weightUnit === 'lbs') ? weightRaw * 0.453592 : weightRaw; var weightG = weightKg * 1000;

// Widmark r factor (body water distribution constant) // Male: 0.68, Female: 0.55 var r = (sex === 'male') ? 0.68 : 0.55;

// Alcohol metabolism rate (g/kg/hr) — average 0.015 g/dL/hr var metabolismRate = 0.015; // g/dL per hour

// Grams of alcohol per standard drink (US standard: 14 g) var gramsPerDrink = 14.0; var totalAlcoholG = drinks * gramsPerDrink;

// Widmark formula: // BAC (g/dL) = (A / (W * r)) * 100 − (beta * t) // where A = alcohol in grams, W = weight in grams, // r = Widmark factor, beta = 0.015 g/dL/hr, t = hours // Note: (A / (W * r)) gives g/g; multiply by 100 to get g/dL

var bac = (totalAlcoholG / (weightG * r)) * 100 - (metabolismRate * hours); bac = Math.max(0, bac); // BAC cannot be negative

// --- Impairment level --- var level = ''; var levelColor = ''; if (bac === 0) { level = 'No measurable alcohol detected.'; levelColor = '#27ae60'; } else if (bac 0) ? (bac / metabolismRate) : 0; var soberHours = Math.floor(timeToSober); var soberMins = Math.round((timeToSober - soberHours) * 60);

var soberStr = (bac === 0)
? 'You are already at 0.00% BAC.': 'Estimated time to reach 0.00% BAC: ' + soberHours + 'h ' + soberMins + 'm (from now).';

resultDiv.innerHTML = '### Estimated BAC: ' + bac.toFixed(3) + '% (g/dL) ' + '' + level + '

' + '' + soberStr + '

' + '⚠️ This is an estimate only. Actual BAC varies with food intake, medications, hydration, and individual metabolism. Never drive after drinking.

'; }

#### Formula

Widmark Formula:

BAC (g/dL) = [A / (W × r)] × 100 − (β × t)

A = total alcohol consumed (grams) — 14 g per US standard drink
W = body weight (grams)
r = Widmark distribution factor — 0.68 (male), 0.55 (female)
β = alcohol elimination rate — 0.015 g/dL per hour (average)
t = hours since drinking began

BAC is floored at 0 (cannot be negative).

#### Assumptions & References

One US standard drink contains 14 grams of pure ethanol (NIAAA definition).
Widmark r values: 0.68 for males, 0.55 for females (Widmark, 1932; updated by Posey & Mozayani, 2007).
Average alcohol elimination rate (β) is 0.015 g/dL/hr; actual range is 0.010–0.020 g/dL/hr depending on the individual.
Legal BAC limit for driving in the US is 0.08 g/dL; limits vary by country and driver category.
This tool is for educational purposes only and should not be used to make decisions about driving or safety.
References: Widmark EMP (1932); NIAAA Standard Drink Definition; Posey & Mozayani, Forensic Science, Medicine, and Pathology (2007).

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