function calculateBAC() {
var numDrinks = parseFloat(document.getElementById('numDrinks').value);
var alcoholPercentage = parseFloat(document.getElementById('alcoholPercentage').value);
var drinkVolumeOz = parseFloat(document.getElementById('drinkVolumeOz').value);
var bodyWeightLbs = parseFloat(document.getElementById('bodyWeightLbs').value);
var genderMale = document.getElementById('genderMale').checked;
var timeElapsedHours = parseFloat(document.getElementById('timeElapsedHours').value);
var resultDiv = document.getElementById('result');
// Input validation
if (isNaN(numDrinks) || numDrinks < 0 ||
isNaN(alcoholPercentage) || alcoholPercentage < 0 ||
isNaN(drinkVolumeOz) || drinkVolumeOz < 0 ||
isNaN(bodyWeightLbs) || bodyWeightLbs <= 0 ||
isNaN(timeElapsedHours) || timeElapsedHours < 0) {
resultDiv.innerHTML = 'Please enter valid positive numbers for all fields.';
return;
}
// Widmark Formula Constants
var r; // Distribution ratio
if (genderMale) {
r = 0.70; // Average for males
} else {
r = 0.58; // Average for females
}
var ethanolDensityGramsPerMl = 0.789; // Density of ethanol
var ozToMl = 29.5735; // 1 fluid ounce = 29.5735 milliliters
var lbsToGrams = 453.592; // 1 pound = 453.592 grams
var eliminationRate = 0.015; // Average BAC elimination rate per hour
// 1. Calculate total pure alcohol consumed in grams
var totalAlcoholOz = numDrinks * (alcoholPercentage / 100) * drinkVolumeOz;
var totalAlcoholMl = totalAlcoholOz * ozToMl;
var totalAlcoholGrams = totalAlcoholMl * ethanolDensityGramsPerMl;
// 2. Convert body weight to grams
var bodyWeightGrams = bodyWeightLbs * lbsToGrams;
// 3. Calculate initial BAC before elimination
var initialBAC = (totalAlcoholGrams / (bodyWeightGrams * r)) * 100;
// 4. Calculate BAC eliminated over time
var eliminatedBAC = eliminationRate * timeElapsedHours;
// 5. Calculate final estimated BAC
var finalBAC = initialBAC – eliminatedBAC;
// Ensure BAC doesn't go below zero
if (finalBAC = 0.08) {
bacMessage = 'Legally impaired in most places. Do NOT drive.';
bacColor = '#d9534f'; // Red
} else if (finalBAC >= 0.05) {
bacMessage = 'Significant impairment. Judgment, coordination, and reaction time are affected. Do NOT drive.';
bacColor = '#f0ad4e'; // Orange
} else if (finalBAC >= 0.02) {
bacMessage = 'Some impairment. Relaxation, slight body warmth, altered mood. Driving ability may be affected.';
bacColor = '#f0ad4e'; // Orange
} else if (finalBAC > 0) {
bacMessage = 'Minimal effects. Still, exercise caution.';
bacColor = '#5cb85c'; // Green
} else {
bacMessage = 'No alcohol detected or fully eliminated.';
bacColor = '#5cb85c'; // Green
}
resultDiv.innerHTML =
'Estimated Blood Alcohol Percentage (BAC): ' + finalBAC.toFixed(3) + '%' +
" + bacMessage + " +
'This is an estimate and should not be used to determine fitness to drive or operate machinery. Individual responses to alcohol vary.';
}
Understanding Your Blood Alcohol Percentage (BAC)
Blood Alcohol Percentage (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. This metric is crucial for understanding the level of intoxication and its potential effects on your body and mind.
How BAC is Calculated
The calculator above uses a simplified version of the Widmark Formula, a widely accepted method for estimating BAC. Several factors influence your BAC:
Number of Drinks: More drinks generally mean a higher BAC.
Alcohol Content & Volume: Drinks with higher alcohol percentages or larger volumes contribute more pure alcohol. A "standard drink" typically contains about 14 grams of pure alcohol (e.g., 12 oz of 5% beer, 5 oz of 12% wine, or 1.5 oz of 40% spirits).
Body Weight: Heavier individuals typically have more body water, which dilutes the alcohol, leading to a lower BAC for the same amount consumed.
Gender: Women generally have less body water and lower levels of the enzyme alcohol dehydrogenase (which metabolizes alcohol) than men. This means women often reach a higher BAC than men after consuming the same amount of alcohol.
Time Elapsed: Your liver metabolizes alcohol at a relatively constant rate, typically around 0.015% per hour. The longer the time since your last drink, the lower your BAC will be.
Food Consumption: Eating before or while drinking can slow the absorption of alcohol into your bloodstream, leading to a slower rise in BAC, though it doesn't prevent intoxication.
BAC Levels and Their Effects
The effects of alcohol vary greatly among individuals, but general guidelines for BAC levels include:
0.02% – 0.03%: Mild relaxation, slight body warmth, altered mood.
0.08% – 0.09%: Legally impaired in most places. Poor muscle coordination, difficulty detecting danger, impaired judgment, memory, and self-control.
0.10% – 0.12%: Significant impairment of motor coordination and loss of judgment. Speech may be slurred.
0.15% – 0.20%: Major loss of balance and motor control. Nausea and vomiting may occur.
0.25% – 0.30%: Severe intoxication. Mental, physical, and sensory functions are severely impaired. Risk of aspiration (choking on vomit).
0.35% – 0.40%: Loss of consciousness, potential for coma. Life-threatening.
> 0.40%: High risk of coma, respiratory arrest, and death.
Important Disclaimer
This Blood Alcohol Percentage Calculator provides an estimate based on average physiological responses. It is not a substitute for professional medical advice or a definitive measure of your fitness to drive or operate machinery. Individual factors like metabolism, medication, fatigue, and health conditions can significantly alter how alcohol affects you. The safest choice is always to avoid driving or engaging in risky activities after consuming any alcohol. If you are concerned about your drinking habits, please seek professional help.