.bac-calculator-container {
font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
max-width: 700px;
margin: 20px auto;
padding: 25px;
border: 1px solid #e0e0e0;
border-radius: 10px;
background-color: #f9f9f9;
box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
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margin-top: 25px;
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transform: translateY(-2px);
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Blood Alcohol Content (BAC) Calculator
Enter the total number of alcoholic beverages you've consumed.
Typical values: Beer (4-6%), Wine (11-14%), Spirits (35-40%).
Standard sizes: Beer (12 oz), Wine (5 oz), Shot of Spirits (1.5 oz).
Gender affects how alcohol is distributed in the body.
Your body weight is a key factor in alcohol concentration.
Enter the hours passed since you started drinking.
Your Estimated BAC: 0.000%
Disclaimer: This BAC calculator provides an estimate based on average formulas and should not be used to determine fitness to drive or operate machinery. Individual results can vary significantly due to many factors including metabolism, food intake, medication, and hydration. Always err on the side of caution.
function calculateBAC() {
var numDrinks = parseFloat(document.getElementById("numDrinks").value);
var drinkAbv = parseFloat(document.getElementById("drinkAbv").value);
var drinkVolumeOz = parseFloat(document.getElementById("drinkVolumeOz").value);
var gender = document.querySelector('input[name="gender"]:checked').value;
var weightLbs = parseFloat(document.getElementById("weightLbs").value);
var timeElapsedHours = parseFloat(document.getElementById("timeElapsedHours").value);
// Input validation
if (isNaN(numDrinks) || numDrinks < 0 ||
isNaN(drinkAbv) || drinkAbv <= 0 ||
isNaN(drinkVolumeOz) || drinkVolumeOz <= 0 ||
isNaN(weightLbs) || weightLbs <= 0 ||
isNaN(timeElapsedHours) || timeElapsedHours < 0) {
document.getElementById("bacResult").innerHTML = "Please enter valid positive numbers for all fields.";
return;
}
// Constants
var ethanolDensityGramsPerMl = 0.789; // Density of ethanol
var ozToMl = 29.5735; // 1 fluid ounce = 29.5735 milliliters
var metabolismRatePerHour = 0.015; // Average BAC reduction per hour
// Widmark's Factor (r)
var rValue;
if (gender === 'male') {
rValue = 0.68; // For men
} else {
rValue = 0.55; // For women
}
// 1. Calculate total pure alcohol consumed
var totalPureAlcoholOz = numDrinks * (drinkAbv / 100) * drinkVolumeOz;
var totalPureAlcoholMl = totalPureAlcoholOz * ozToMl;
var totalPureAlcoholGrams = totalPureAlcoholMl * ethanolDensityGramsPerMl;
// 2. Convert body weight to grams
var weightGrams = weightLbs * 453.592; // 1 lb = 453.592 grams
// 3. Calculate initial BAC using Widmark's Formula
// BAC = (Alcohol in grams / (Body weight in grams * r)) * 100
var initialBAC = (totalPureAlcoholGrams / (weightGrams * rValue)) * 100;
// 4. Account for alcohol metabolism over time
var currentBAC = initialBAC – (metabolismRatePerHour * timeElapsedHours);
// Ensure BAC doesn't go below zero
if (currentBAC < 0) {
currentBAC = 0;
}
document.getElementById("bacResult").innerHTML = currentBAC.toFixed(3) + "%";
}
Understanding Your Blood Alcohol Content (BAC)
Blood Alcohol Content (BAC) is a measure of the amount of alcohol in your blood, expressed as a percentage. For example, a BAC of 0.08% means that there are 0.08 grams of alcohol for every 100 milliliters of blood. Understanding your BAC is crucial for making responsible decisions about drinking, especially concerning driving and personal safety.
How is BAC Calculated?
The calculator above uses a modified version of the Widmark formula, a widely accepted method for estimating BAC. This formula takes into account several key factors:
- Number of Drinks: The more alcohol you consume, the higher your BAC will be.
- Alcohol by Volume (ABV) and Drink Volume: These determine the total amount of pure alcohol ingested. A standard drink in the U.S. typically contains about 0.6 fluid ounces (14 grams) of pure alcohol, found in 12 oz of regular beer (5% ABV), 5 oz of wine (12% ABV), or 1.5 oz of distilled spirits (40% ABV).
- Body Weight: A heavier person generally has more body water, which dilutes the alcohol, leading to a lower BAC for the same amount of alcohol consumed compared to a lighter person.
- Gender: Women typically have less body water and higher body fat percentages than men, meaning alcohol is less diluted in their bodies. They also tend to have lower levels of alcohol dehydrogenase, an enzyme that metabolizes alcohol, leading to higher BACs even when consuming the same amount as a man of similar weight.
- Time Elapsed: Your liver metabolizes alcohol at a relatively constant rate, typically reducing your BAC by about 0.015% per hour. The longer the time since your first drink, the more alcohol your body has processed.
Factors That Can Influence BAC (Beyond the Calculator)
While this calculator provides a good estimate, many other factors can influence your actual BAC:
- Food Intake: Drinking on an empty stomach allows alcohol to be absorbed into the bloodstream much faster, leading to a quicker and higher BAC peak. Food slows down this absorption.
- Medication: Certain medications can interact with alcohol, affecting its absorption, metabolism, and overall impact on your body.
- Hydration: Dehydration can concentrate alcohol in your system.
- Rate of Consumption: Drinking quickly will lead to a higher BAC than sipping the same amount of alcohol over a longer period.
- Fatigue and Stress: These can amplify the effects of alcohol, even at lower BAC levels.
- Genetics: Individual metabolic rates can vary.
Legal Limits and Impairment
In most U.S. states, the legal limit for driving is a BAC of 0.08%. However, impairment can begin at much lower levels:
- 0.02% BAC: Some loss of judgment, altered mood, decline in visual function, and ability to perform two tasks at once.
- 0.05% BAC: Reduced coordination, difficulty steering, reduced ability to track moving objects, difficulty responding to emergencies.
- 0.08% BAC: Poor muscle coordination, difficulty detecting danger, impaired judgment, reduced information processing capability.
- 0.10% BAC: Clear deterioration of reaction time and control, slurred speech, poor coordination.
It's important to remember that even small amounts of alcohol can impair your ability to drive safely. The safest choice is always to designate a sober driver or arrange for alternative transportation if you plan to drink.