Estimate your Blood Alcohol Content (BAC) based on your weight, gender, drinks consumed, and time elapsed.
Male
Female
Understanding Your Blood Alcohol Content (BAC)
Blood Alcohol Content (BAC) is a measurement of the amount of alcohol present in your bloodstream. It's typically expressed as a percentage. For example, a BAC of 0.08% means that 0.08% of your blood volume is alcohol. Understanding your BAC is crucial for making informed decisions about driving, your health, and your safety.
How BAC is Calculated
The Widmark formula is a commonly used method to estimate BAC. While it provides a good approximation, it's important to remember that individual metabolism, food intake, hydration levels, and other factors can influence actual BAC. The formula generally looks like this:
BAC = (A / (W * r)) * 100 – (E * 9.8 / (W * r))
Where:
A = Total grams of alcohol consumed.
W = Body weight in kilograms.
r = Alcohol distribution ratio (approx. 0.68 for men, 0.55 for women).
E = Total grams of alcohol eliminated (calculated based on hours elapsed and the body's metabolic rate).
The calculator above simplifies this by:
Estimating grams of alcohol from standard drinks. A standard drink contains about 14 grams of pure alcohol (this can vary slightly by country).
Converting your weight from pounds to kilograms (1 lb = 0.453592 kg).
Using the gender-specific alcohol distribution ratio (r).
Estimating alcohol elimination based on the typical rate of 0.015% per hour.
Standard Drinks Explained
A "standard drink" is a measure of alcohol. In the United States, a standard drink contains about 14 grams (0.6 fluid ounces or 1.2 tablespoons) of pure alcohol. This is equivalent to:
12 ounces of regular beer (about 5% alcohol)
5 ounces of wine (about 12% alcohol)
1.5 ounces of distilled spirits (about 40% alcohol, or 80 proof)
Factors Affecting BAC
The BAC calculator provides an estimate. Several factors can influence your actual BAC:
Food Intake: Drinking on an empty stomach leads to faster alcohol absorption and higher BAC.
Metabolism: Individual metabolic rates vary.
Hydration: Dehydration can concentrate alcohol in the bloodstream.
Medications: Certain medications can interact with alcohol.
Fat vs. Muscle: Alcohol distributes differently in body fat and muscle tissue.
Legal Limits and Safety
In most places, driving with a BAC of 0.08% or higher is illegal. Even lower BAC levels can impair judgment and reaction time, increasing the risk of accidents. It's always safest to avoid alcohol if you plan to drive or operate machinery. If you've been drinking, arrange for a designated driver, use ride-sharing services, or stay overnight.
Disclaimer: This calculator is for informational purposes only and should not be used as a substitute for professional medical or legal advice. Actual BAC can vary.
function calculateBAC() {
var weightLbs = parseFloat(document.getElementById("weight").value);
var gender = document.getElementById("gender").value;
var drinks = parseFloat(document.getElementById("drinks").value);
var hours = parseFloat(document.getElementById("hours").value);
var resultDiv = document.getElementById("result");
// Clear previous results and error messages
resultDiv.innerHTML = "";
// Input validation
if (isNaN(weightLbs) || weightLbs <= 0) {
resultDiv.innerHTML = "Please enter a valid weight.";
resultDiv.style.backgroundColor = "#dc3545"; // Red for error
return;
}
if (isNaN(drinks) || drinks < 0) {
resultDiv.innerHTML = "Please enter a valid number of drinks.";
resultDiv.style.backgroundColor = "#dc3545";
return;
}
if (isNaN(hours) || hours < 0) {
resultDiv.innerHTML = "Please enter a valid number of hours.";
resultDiv.style.backgroundColor = "#dc3545";
return;
}
// Constants
var gramsPerStandardDrink = 14; // grams of pure alcohol in a standard drink
var weightKgMultiplierMale = 0.68; // Alcohol distribution ratio for males
var weightKgMultiplierFemale = 0.55; // Alcohol distribution ratio for females
var eliminationRatePerHour = 0.015; // BAC percentage eliminated per hour
// Convert weight from lbs to kg
var weightKg = weightLbs * 0.453592;
// Determine alcohol distribution ratio based on gender
var distributionRatio = (gender === "male") ? weightKgMultiplierMale : weightKgMultiplierFemale;
// Calculate total grams of alcohol consumed
var totalAlcoholGrams = drinks * gramsPerStandardDrink;
// Calculate BAC using a simplified Widmark-like formula
// The formula for this calculator is based on a common estimation:
// BAC = (Total Alcohol Grams / (Body Weight in Kg * Distribution Ratio)) * 100
// Then subtract the alcohol eliminated over time.
// Initial BAC estimation before elimination
var initialBAC = (totalAlcoholGrams / (weightKg * distributionRatio));
// Calculate alcohol eliminated over time
var alcoholEliminated = hours * eliminationRatePerHour;
// Calculate final BAC
var finalBAC = initialBAC – alcoholEliminated;
// Ensure BAC doesn't go below zero
if (finalBAC < 0) {
finalBAC = 0;
}
// Format the result
var formattedBAC = finalBAC.toFixed(3); // Display with 3 decimal places
resultDiv.innerHTML = `${formattedBAC}% BAC` + "Blood Alcohol Content";
resultDiv.style.backgroundColor = "var(–success-green)"; // Green for success
// Add some interpretation based on common legal limits
var interpretation = "";
if (parseFloat(formattedBAC) >= 0.08) {
interpretation = "This level is illegal to drive in most jurisdictions and indicates significant impairment.";
resultDiv.style.backgroundColor = "#ffc107"; // Orange for warning
resultDiv.style.color = "var(–dark-text)";
} else if (parseFloat(formattedBAC) >= 0.05) {
interpretation = "Significant impairment. Driving is not recommended.";
resultDiv.style.backgroundColor = "#fd7e14"; // Slightly less warning color
resultDiv.style.color = "white";
} else if (parseFloat(formattedBAC) > 0) {
interpretation = "Impairment is possible. Exercise caution.";
} else {
interpretation = "No significant alcohol detected.";
}
var interpretationDiv = document.createElement('div');
interpretationDiv.style.fontSize = '0.8em';
interpretationDiv.style.marginTop = '10px';
interpretationDiv.style.fontWeight = 'normal';
interpretationDiv.textContent = interpretation;
resultDiv.appendChild(interpretationDiv);
}