Blood Alcohol Content Calculator

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Blood Alcohol Content (BAC) Calculator

Male Female
(1 drink = 12oz beer, 5oz wine, or 1.5oz spirit)

Estimated BAC: 0.00%

Disclaimer: This calculator is for informational purposes only. Many factors affect BAC including metabolism, food intake, and medication. Never drink and drive.

function calculateBAC() { var gender = document.getElementById('gender').value; var weight = parseFloat(document.getElementById('weight').value); var drinks = parseFloat(document.getElementById('drinks').value); var hours = parseFloat(document.getElementById('hours').value); if (isNaN(weight) || isNaN(drinks) || isNaN(hours) || weight <= 0) { alert("Please enter valid numbers for weight, drinks, and time."); return; } // Widmark Formula: BAC = [ (Alcohol in grams / (Weight in grams * r)) * 100 ] – (Elapsed time * 0.015) // 1 standard drink is approx 14 grams of pure alcohol (US standard) var alcoholGrams = drinks * 14; var weightGrams = weight * 1000; // Gender distribution constant (r) var r = (gender === 'male') ? 0.68 : 0.55; // Calculate raw BAC var rawBAC = (alcoholGrams / (weightGrams * r)) * 100; // Subtract metabolism (average 0.015% per hour) var totalBAC = rawBAC – (hours * 0.015); if (totalBAC < 0) totalBAC = 0; var resultArea = document.getElementById('result-area'); var bacDisplay = document.getElementById('bac-value'); var riskDisplay = document.getElementById('risk-level'); resultArea.style.display = 'block'; bacDisplay.innerText = totalBAC.toFixed(3); if (totalBAC === 0) { resultArea.style.backgroundColor = '#d4edda'; riskDisplay.innerText = "Sober / Negligible Alcohol"; riskDisplay.style.color = '#155724'; } else if (totalBAC < 0.05) { resultArea.style.backgroundColor = '#fff3cd'; riskDisplay.innerText = "Mild Impairment / Buzz"; riskDisplay.style.color = '#856404'; } else if (totalBAC < 0.08) { resultArea.style.backgroundColor = '#ffeeba'; riskDisplay.innerText = "Increased Impairment – Approaching Legal Limit"; riskDisplay.style.color = '#856404'; } else { resultArea.style.backgroundColor = '#f8d7da'; riskDisplay.innerText = "Legally Intoxicated – High Risk / Do Not Drive"; riskDisplay.style.color = '#721c24'; } }

Understanding Blood Alcohol Content (BAC)

Blood Alcohol Content, or BAC, is a measurement of the percentage of alcohol present in your bloodstream. For example, a BAC of 0.08% means that there is 0.08 grams of alcohol for every 100 milliliters of blood. Understanding this metric is vital for safety, legal compliance, and making responsible decisions regarding alcohol consumption.

The Widmark Formula

Our calculator utilizes the Widmark Formula, which is the scientific standard for estimating intoxication levels. This formula takes into account the mass of alcohol consumed, the body weight of the individual, the gender-specific distribution of water in the body (the "r" constant), and the rate at which the liver metabolizes alcohol over time.

Key Factors Affecting Your BAC

  • Body Weight: Individuals with higher body mass generally have more blood and water in their systems, which can dilute alcohol more than in lighter individuals.
  • Biological Sex: Men typically have a higher percentage of body water (approx. 68%) compared to women (approx. 55%), meaning women often reach higher BAC levels after consuming the same amount of alcohol.
  • Time: The human body metabolizes alcohol at a constant rate, roughly 0.015% BAC per hour. You cannot speed this process up with coffee, cold showers, or exercise.
  • Food Consumption: Eating before or while drinking slows the absorption of alcohol into the bloodstream, though it does not prevent the eventual peak BAC.

Standard Drink Sizes

In the United States, a "standard drink" contains roughly 14 grams of pure alcohol. This is typically found in:

  • 12 ounces of regular beer (about 5% alcohol).
  • 5 ounces of wine (about 12% alcohol).
  • 1.5 ounces of distilled spirits (about 40% alcohol).

Realistic Scenario Example

Imagine a 180 lb (81.6 kg) male who consumes 3 standard beers over the course of 2 hours.

  1. Alcohol Grams: 3 drinks × 14g = 42g of alcohol.
  2. Distribution: 81.6kg × 1000 = 81,600g body weight. (81,600 × 0.68) = 55,488.
  3. Peak BAC: (42 / 55,488) × 100 = 0.075%.
  4. Metabolism: After 2 hours, subtract (2 × 0.015) = 0.03%.
  5. Estimated BAC: 0.045%.

A Critical Safety Note

While this calculator provides a mathematical estimate, it should never be used to determine if it is safe to drive. Alcohol affects everyone differently. Factors such as fatigue, medication, and individual metabolic rates can make a person impaired even if their BAC is below the legal limit of 0.08%. If you have been drinking, the safest choice is always to use a designated driver or ride-sharing service.

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