Blood Alcohol Content (BAC) Calculator
Estimate your Blood Alcohol Content (BAC) based on your consumption, weight, gender, and time elapsed. This calculator uses the Widmark formula and provides an approximate value. Always drink responsibly.
Understanding 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 0.10% means that there are 0.10 grams of alcohol for every 100 milliliters of blood. BAC is a critical indicator of intoxication and is used legally to determine impairment, especially for driving.
How is BAC Calculated? The Widmark Formula
The calculator above uses a modified version of the Widmark formula, a widely accepted method for estimating BAC. The core principle is to determine the total amount of alcohol consumed and distribute it across the body's water content. Key factors in this calculation include:
- Total Alcohol Consumed: This is derived from the number of drinks, their volume, and their alcohol by volume (ABV) percentage.
- Body Weight: Heavier individuals generally have more body water, which dilutes the alcohol, leading to a lower BAC for the same amount of alcohol consumed.
- Gender: Women typically have a lower percentage of body water and higher body fat compared to men of the same weight. This means alcohol is less diluted in women's bodies, often resulting in a higher BAC. The Widmark formula uses a distribution ratio ('r' value) that accounts for this difference (approximately 0.68 for men and 0.55 for women).
- Time Elapsed: The human body metabolizes alcohol at a relatively constant rate, typically around 0.015% per hour. The calculator subtracts the alcohol eliminated over time from the initial peak BAC.
Factors Influencing BAC (Beyond the Calculator)
While the calculator provides a good estimate, several other factors can influence your actual BAC:
- Food Consumption: Eating before or while drinking slows the absorption of alcohol into the bloodstream, leading to a lower peak BAC.
- Medications: Certain medications can interact with alcohol, intensifying its effects or altering its metabolism.
- Hydration Level: Dehydration can lead to a higher BAC.
- Genetics and Metabolism: Individual differences in liver enzyme activity can affect how quickly alcohol is processed.
- Rate of Consumption: Drinking quickly will lead to a higher BAC than consuming the same amount over a longer period.
BAC Levels and Their Effects
Understanding the effects associated with different BAC levels is crucial for responsible drinking:
- 0.00% – 0.02%: Minimal effects, slight mood alteration, no significant impairment.
- 0.03% – 0.05%: Mild euphoria, relaxation, impaired judgment, reduced coordination. Legal limit for driving in some countries (e.g., 0.05% in some US states, 0.02% for commercial drivers).
- 0.06% – 0.09%: Impaired judgment, reduced coordination, slurred speech, decreased reaction time. Legal limit for driving in most US states (0.08%).
- 0.10% – 0.15%: Significant impairment of motor control, reaction time, and judgment. Obvious intoxication.
- 0.16% – 0.20%: Nausea, vomiting, severe motor impairment, "blackouts" may occur.
- 0.21% – 0.30%: Loss of consciousness, potential for alcohol poisoning, severe disorientation.
- 0.31% and above: Severe alcohol poisoning, coma, potential respiratory depression and death. This level is extremely dangerous.
Disclaimer and Responsible Drinking
This BAC calculator is for informational and educational purposes only and should not be used to determine fitness to drive or operate machinery. Individual responses to alcohol can vary significantly. The only truly accurate way to measure BAC is through a breathalyzer or blood test. If you choose to drink, do so responsibly, know your limits, and never drink and drive. If you or someone you know needs help with alcohol, please seek professional assistance.
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function calculateBAC() {
var numDrinks = parseFloat(document.getElementById('numDrinks').value);
var drinkVolume = parseFloat(document.getElementById('drinkVolume').value);
var alcoholPercentage = parseFloat(document.getElementById('alcoholPercentage').value);
var bodyWeight = parseFloat(document.getElementById('bodyWeight').value);
var gender = document.querySelector('input[name="gender"]:checked').value;
var timeElapsed = parseFloat(document.getElementById('timeElapsed').value);
var bacResultElement = document.getElementById('bacResult');
var bacInterpretationElement = document.getElementById('bacInterpretation');
// Input validation
if (isNaN(numDrinks) || numDrinks < 0 ||
isNaN(drinkVolume) || drinkVolume <= 0 ||
isNaN(alcoholPercentage) || alcoholPercentage 100 ||
isNaN(bodyWeight) || bodyWeight <= 0 ||
isNaN(timeElapsed) || timeElapsed < 0) {
bacResultElement.innerHTML = "Invalid Input";
bacInterpretationElement.innerHTML = "Please enter valid positive numbers for all fields.";
return;
}
// Constants
var alcoholDensity = 0.789; // g/mL
var ozToMl = 29.5735; // 1 fluid ounce = 29.5735 mL
var lbsToGrams = 453.592; // 1 lb = 453.592 grams
var eliminationRate = 0.015; // % per hour
// Calculate total alcohol consumed in grams
var totalAlcoholMl = numDrinks * drinkVolume * ozToMl * (alcoholPercentage / 100);
var totalAlcoholGrams = totalAlcoholMl * alcoholDensity;
// Determine distribution ratio (r) based on gender
var r;
if (gender === 'male') {
r = 0.68; // Average for men
} else {
r = 0.55; // Average for women
}
// Calculate body weight in grams
var bodyWeightGrams = bodyWeight * lbsToGrams;
// Calculate initial BAC using Widmark formula
// BAC = [Alcohol_in_grams / (Body_weight_in_grams * r)] * 100
var initialBAC = (totalAlcoholGrams / (bodyWeightGrams * r)) * 100;
// Account for alcohol elimination over time
var currentBAC = initialBAC – (eliminationRate * timeElapsed);
// Ensure BAC doesn't go below zero
if (currentBAC = 0.31) {
interpretation = "
Extremely Dangerous: Severe alcohol poisoning, coma, potential death. Seek immediate medical attention.";
} else if (currentBAC >= 0.21) {
interpretation = "
Very High Impairment: Loss of consciousness, potential for alcohol poisoning. High risk.";
} else if (currentBAC >= 0.16) {
interpretation = "
Significant Impairment: Nausea, vomiting, severe motor impairment, 'blackouts' may occur. Do not drive.";
} else if (currentBAC >= 0.10) {
interpretation = "
High Impairment: Significant impairment of motor control, reaction time, and judgment. Clearly intoxicated. Do not drive.";
} else if (currentBAC >= 0.08) {
interpretation = "
Legally Impaired (Most US States): Impaired judgment, reduced coordination, slurred speech, decreased reaction time. Do not drive.";
} else if (currentBAC >= 0.05) {
interpretation = "
Impaired: Mild euphoria, relaxation, impaired judgment, reduced coordination. Do not drive.";
} else if (currentBAC >= 0.03) {
interpretation = "
Mild Effects: Slight mood alteration, relaxation, minor impairment of judgment.";
} else if (currentBAC > 0) {
interpretation = "
Minimal Effects: Little to no noticeable effect, slight mood alteration.";
} else {
interpretation = "
Sober: No alcohol detected or all alcohol has been metabolized.";
}
bacInterpretationElement.innerHTML = interpretation;
}
// Calculate on page load for initial values
window.onload = calculateBAC;