Estimate your Blood Alcohol Content based on your body weight, gender, and consumption.
Male
Female
Your BAC will be displayed here.
Understanding the BAC Content Calculator
The Blood Alcohol Content (BAC) calculator is a tool designed to provide an estimate of the concentration of alcohol in a person's bloodstream. It's important to understand that this is an approximation, and actual BAC can vary due to numerous individual factors not precisely accounted for by simple formulas.
How the Calculation Works
The most commonly used formulas for estimating BAC are variations of the Widmark formula. A simplified version considers:
Body Weight: Heavier individuals generally have more body water to distribute alcohol, potentially leading to a lower BAC than a lighter person consuming the same amount.
Number of Standard Drinks: A standard drink is typically defined as 10 grams (or about 12.5 ml) of pure alcohol. This equates to:
A standard glass of wine (approx. 150 ml or 5 oz)
A standard beer (approx. 350 ml or 12 oz)
A shot of spirits (approx. 40 ml or 1.5 oz)
Time Elapsed: Alcohol is metabolized by the body over time, primarily by the liver. The average rate of alcohol elimination is about 0.015% per hour.
Gender: Biological differences in body composition and the enzyme alcohol dehydrogenase (ADH) mean that, on average, women tend to reach higher BAC levels than men when consuming the same amount of alcohol. Men typically have a higher percentage of body water.
The Simplified Formula
A common approximation for BAC is:
BAC = (A / (W * r)) * 100 - (E * H)
Where:
A = Total grams of alcohol consumed. This is calculated by multiplying the number of standard drinks by the grams of alcohol per standard drink (usually 10g).
W = Body weight in kilograms.
r = Alcohol distribution ratio (or Widmark factor):
0.68 for males
0.55 for females
This factor represents the proportion of body weight that is water.
E = Alcohol elimination rate (approximately 0.015% per hour).
H = Time elapsed since the first drink, in hours.
Note: The calculator simplifies grams of alcohol to a unitless "standard drink" input and uses a standard value for alcohol per drink and the elimination rate.
Disclaimer
This calculator provides an estimate for informational purposes only. It is not a substitute for professional legal or medical advice. Actual BAC can be influenced by factors such as food intake, metabolism, medications, hydration levels, and personal health conditions. Never drink and drive.
function calculateBAC() {
var weight = parseFloat(document.getElementById("weight").value);
var drinks = parseFloat(document.getElementById("drinks").value);
var hours = parseFloat(document.getElementById("hours").value);
var gender = document.getElementById("gender").value;
var resultDiv = document.getElementById("result");
// Validate inputs
if (isNaN(weight) || weight <= 0 ||
isNaN(drinks) || drinks < 0 ||
isNaN(hours) || hours < 0) {
resultDiv.innerHTML = "Please enter valid positive numbers for all fields.";
return;
}
// Constants
var gramsPerDrink = 10; // Approximate grams of alcohol per standard drink
var alcoholEliminationRate = 0.015; // Approximate BAC decrease per hour
// Alcohol distribution ratios
var r;
if (gender === "male") {
r = 0.68;
} else { // female
r = 0.55;
}
// Total grams of alcohol consumed
var totalGramsAlcohol = drinks * gramsPerDrink;
// Calculate BAC using a simplified Widmark formula
// BAC = (A / (W * r)) * 100 – (E * H)
// We are normalizing the (A / (W * r)) * 100 part based on a standard drink's contribution
// and then subtracting the elimination over time.
// A more direct implementation for online calculators often looks like this:
// BAC = (Total Alcohol in grams) / (Body Water in grams) * 100%
// Body Water = Body Weight * r
// Let's use a common formula often seen in online calculators that directly relates drinks to BAC
// based on gender and weight, then adjusts for time.
var bac;
if (gender === "male") {
bac = (drinks * 1.2) / (weight * 0.68) – (hours * 0.015);
} else { // female
bac = (drinks * 1.2) / (weight * 0.55) – (hours * 0.015);
}
// Ensure BAC doesn't go below zero
if (bac < 0) {
bac = 0;
}
// Display result
resultDiv.innerHTML = "Estimated BAC: " + bac.toFixed(3);
}