Blood Alcohol Content (BAC) Level Calculator
Use this calculator to estimate your Blood Alcohol Content (BAC) level. BAC is a measure of the amount of alcohol in your blood, expressed as a percentage. Understanding your BAC can help you make informed decisions about drinking and driving, though this calculator provides an estimate and should not be used to determine fitness to drive or operate machinery.
Understanding Blood Alcohol Content (BAC)
Blood Alcohol Content (BAC) is a critical metric that quantifies the amount of alcohol present in your bloodstream. It's typically expressed as a percentage, for example, a BAC of 0.08% means there are 0.08 grams of alcohol for every 100 milliliters of blood. This level is often the legal limit for driving in many countries.
Factors Influencing BAC
- Number of Drinks: More drinks generally lead to higher BAC.
- Body Weight: Heavier individuals typically have more body water, which dilutes the alcohol, resulting in a lower BAC for the same amount of alcohol consumed.
- Gender: Women generally have less body water and lower levels of alcohol dehydrogenase (an enzyme that metabolizes alcohol) than men, leading to higher BACs even when consuming the same amount of alcohol.
- Time Elapsed: The liver metabolizes alcohol at a relatively constant rate (approximately 0.015% per hour). The longer the time since your last drink, the lower your BAC will be.
- Food Consumption: Eating before or while drinking can slow the absorption of alcohol into the bloodstream, leading to a lower peak BAC.
- Medications: Certain medications can interact with alcohol, affecting its absorption and metabolism.
Legal Limits and Impairment
In most parts of the United States, the legal limit for driving is a BAC of 0.08%. However, impairment can begin at much lower levels. Even a BAC of 0.02% can affect judgment and visual function. As BAC increases, so does the level of impairment, affecting coordination, reaction time, and decision-making abilities significantly.
Disclaimer
This BAC calculator provides an estimate based on common formulas and averages. Individual results can vary significantly due to unique physiological factors, metabolism rates, and other variables not accounted for in this simplified model. This tool is for informational purposes only and should NOT be used to determine your fitness to drive, operate machinery, or engage in any activity requiring sobriety. Always err on the side of caution and never drink and drive.
function calculateBAC() { var numDrinks = parseFloat(document.getElementById("numDrinks").value); var bodyWeightLbs = parseFloat(document.getElementById("bodyWeight").value); var gender = document.getElementById("gender").value; var timeElapsedHours = parseFloat(document.getElementById("timeElapsed").value); var resultDiv = document.getElementById("bacResult"); // Input validation if (isNaN(numDrinks) || numDrinks < 0) { resultDiv.innerHTML = "Please enter a valid number of drinks."; return; } if (isNaN(bodyWeightLbs) || bodyWeightLbs <= 0) { resultDiv.innerHTML = "Please enter a valid body weight."; return; } if (isNaN(timeElapsedHours) || timeElapsedHours < 0) { resultDiv.innerHTML = "Please enter a valid time elapsed."; return; } // Constants for Widmark Formula var standardAlcoholGrams = 14; // Approximately 14 grams of pure alcohol per standard drink in the US var bodyWeightGrams = bodyWeightLbs * 453.592; // Convert lbs to grams var genderRatio; // 'r' factor in Widmark formula if (gender === "male") { genderRatio = 0.68; } else { // female genderRatio = 0.55; } var metabolismRate = 0.015; // Average alcohol elimination rate per hour (0.015% per hour) // Calculate total alcohol consumed in grams var totalAlcoholGrams = numDrinks * standardAlcoholGrams; // Calculate peak BAC using Widmark Formula: BAC = (Alcohol_grams / (Body_weight_grams * r)) * 100 var peakBAC = (totalAlcoholGrams / (bodyWeightGrams * genderRatio)) * 100; // Account for alcohol metabolized over time var metabolizedAlcohol = timeElapsedHours * metabolismRate; var currentBAC = peakBAC – metabolizedAlcohol; // Ensure BAC doesn't go below zero if (currentBAC < 0) { currentBAC = 0; } // Display result var bacString = currentBAC.toFixed(3); // Format to 3 decimal places var interpretation = ""; if (currentBAC === 0) { interpretation = "You likely have no alcohol in your system."; } else if (currentBAC < 0.02) { interpretation = "Minimal impairment, but effects can still be felt."; } else if (currentBAC < 0.05) { interpretation = "Relaxation, slight body warmth, altered judgment. Legal limit for driving in some countries."; } else if (currentBAC < 0.08) { interpretation = "Reduced coordination, impaired judgment, difficulty steering. Nearing the legal limit for driving in many places."; } else if (currentBAC < 0.10) { interpretation = "Significant impairment of motor skills, judgment, and reaction time. This is the legal limit for driving in most of the U.S."; } else if (currentBAC < 0.15) { interpretation = "Gross impairment, slurred speech, blurred vision, loss of balance."; } else { interpretation = "Severe impairment, significant loss of control, potential for nausea and vomiting. Extremely dangerous for driving or any complex task."; } resultDiv.innerHTML = "