function calculateBAC() {
var weightLbs = parseFloat(document.getElementById('weightLbs').value);
var gender = document.getElementById('gender').value;
var numDrinks = parseFloat(document.getElementById('numDrinks').value);
var timeElapsedHours = parseFloat(document.getElementById('timeElapsedHours').value);
var bacResultDiv = document.getElementById('bacResult');
// Input validation
if (isNaN(weightLbs) || weightLbs <= 0) {
bacResultDiv.innerHTML = 'Please enter a valid weight.';
return;
}
if (isNaN(numDrinks) || numDrinks < 0) {
bacResultDiv.innerHTML = 'Please enter a valid number of drinks.';
return;
}
if (isNaN(timeElapsedHours) || timeElapsedHours < 0) {
bacResultDiv.innerHTML = 'Please enter a valid time elapsed.';
return;
}
// Widmark Factor (r) – distribution ratio
var r;
if (gender === 'male') {
r = 0.68; // Average for males
} else {
r = 0.55; // Average for females
}
// Alcohol content per standard drink (approx. 14 grams of pure alcohol)
// 1 standard drink = 12 oz beer (5% ABV), 5 oz wine (12% ABV), 1.5 oz spirits (40% ABV)
var alcoholGramsPerDrink = 14;
// Total alcohol consumed in grams
var totalAlcoholGrams = numDrinks * alcoholGramsPerDrink;
// Convert weight from lbs to grams
var weightGrams = weightLbs * 453.592; // 1 lb = 453.592 grams
// Calculate initial BAC (before elimination)
// BAC = (Alcohol in grams / (Body Weight in grams * r)) * 100
var initialBAC = (totalAlcoholGrams / (weightGrams * r)) * 100;
// Alcohol elimination rate (average 0.015% per hour)
var eliminationRatePerHour = 0.015;
// Calculate BAC reduction due to metabolism
var eliminatedBAC = timeElapsedHours * eliminationRatePerHour;
// Final estimated BAC
var finalBAC = initialBAC – eliminatedBAC;
// Ensure BAC doesn't go below zero
if (finalBAC < 0) {
finalBAC = 0;
}
bacResultDiv.innerHTML = 'Your estimated Blood Alcohol Content (BAC) is: ' + finalBAC.toFixed(3) + '%';
if (finalBAC >= 0.08) {
bacResultDiv.innerHTML += 'This BAC level is generally considered legally impaired in most places. Please do not drive.';
} else if (finalBAC > 0) {
bacResultDiv.innerHTML += 'Even at lower BAC levels, your judgment and reaction time can be affected. Always drink responsibly.';
} else {
bacResultDiv.innerHTML += 'Your BAC is estimated to be 0%. Always ensure you are sober before driving or operating machinery.';
}
}
.calculator-container {
background-color: #f9f9f9;
border: 1px solid #ddd;
padding: 20px;
border-radius: 8px;
max-width: 600px;
margin: 20px auto;
font-family: Arial, sans-serif;
}
.calculator-container h2 {
text-align: center;
color: #333;
margin-bottom: 20px;
}
.calc-input-group {
margin-bottom: 15px;
}
.calc-input-group label {
display: block;
margin-bottom: 5px;
font-weight: bold;
color: #555;
}
.calc-input-group input[type="number"],
.calc-input-group select {
width: calc(100% – 22px);
padding: 10px;
border: 1px solid #ccc;
border-radius: 4px;
box-sizing: border-box;
}
.calc-button {
display: block;
width: 100%;
padding: 12px;
background-color: #007bff;
color: white;
border: none;
border-radius: 4px;
font-size: 18px;
cursor: pointer;
transition: background-color 0.3s ease;
margin-top: 20px;
}
.calc-button:hover {
background-color: #0056b3;
}
.calc-result {
margin-top: 25px;
padding: 15px;
border: 1px solid #e0e0e0;
border-radius: 4px;
background-color: #e9ecef;
text-align: center;
font-size: 1.1em;
color: #333;
}
.calc-result p {
margin: 5px 0;
}
.calc-result .error {
color: #dc3545;
font-weight: bold;
}
.calc-result .warning {
color: #ffc107;
font-weight: bold;
}
.calc-result .info {
color: #17a2b8;
}
.calc-result .success {
color: #28a745;
}
Understanding Your Blood Alcohol Content (BAC)
The Blood Alcohol Content (BAC) calculator is a tool designed to estimate the concentration of alcohol in your bloodstream. This percentage is a critical indicator of how intoxicated you are and is used legally to define impairment for activities like driving.
What is BAC?
BAC is expressed as a percentage of alcohol per unit of blood. For example, a BAC of 0.08% means there are 0.08 grams of alcohol for every 100 milliliters of blood. This level is the legal limit for driving under the influence (DUI) in most parts of the United States and many other countries.
How is BAC Calculated?
Our calculator uses a widely accepted formula, often referred to as the Widmark formula, which takes into account several key factors:
Body Weight: Generally, a heavier person has more body water to dilute the alcohol, leading to a lower BAC than a lighter person consuming the same amount.
Gender: Biological differences, such as average body water content and the presence of certain enzymes, mean that women typically reach a higher BAC than men after consuming the same amount of alcohol. This is accounted for by the "Widmark factor" (r-value), which is lower for females.
Number of Standard Drinks: The more alcohol consumed, the higher the BAC. A "standard drink" is defined as containing approximately 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)
It's crucial to understand that different beverages have varying alcohol percentages and serving sizes, so what you perceive as "one drink" might actually be more than one standard drink.
Time Elapsed Since First Drink: The human body metabolizes alcohol at a relatively constant rate, typically around 0.015% BAC per hour. This means that over time, your BAC will decrease as your liver processes the alcohol. The calculator subtracts the estimated amount of alcohol metabolized over the hours you've been drinking.
Factors Not Included (But Important to Consider):
While this calculator provides a good estimate, individual BAC can be influenced by other factors not included in this simplified model:
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, metabolism, or intensifying its effects.
Fatigue and Stress: These can amplify the effects of alcohol, making you feel more impaired even at lower BAC levels.
Individual Metabolism: While an average elimination rate is used, individual metabolic rates can vary.
Hydration Level: Dehydration can affect how your body processes alcohol.
Legal and Safety Implications
A BAC of 0.08% is the legal limit for driving in most U.S. states. However, impairment can begin at much lower levels. Even a BAC of 0.02% can affect judgment and visual function. It is always safest to avoid driving after consuming any alcohol. This calculator is for informational purposes only and should not be used to determine fitness to drive or operate machinery. Always prioritize safety and responsible choices.
Responsible Drinking
Understanding your BAC can help you make more informed decisions about alcohol consumption. Always:
Drink in moderation.
Know what a standard drink is.
Eat food before and during drinking.
Stay hydrated with non-alcoholic beverages.
Never drink and drive. Designate a sober driver, use public transportation, or call a ride-sharing service.