Disclaimer: This is an estimate based on the Widmark formula. Many factors like metabolism, food, and medication affect actual BAC. Never drink and drive.
Understanding Blood Alcohol Content (BAC)
Blood Alcohol Content (BAC) is the metric used to measure the amount of alcohol in a person's bloodstream. It is expressed as a percentage. For example, a BAC of 0.08% means that there are 0.08 grams of alcohol for every 100 milliliters of blood.
This "Most Accurate BAC Calculator" utilizes the Widmark Formula, which is the scientific gold standard for forensic alcohol estimation. While no online tool can replace a professional breathalyzer or blood test, the Widmark method provides the most reliable mathematical approximation available.
The Widmark Formula Explained
The calculation is based on several key variables:
Alcohol Dose: Calculated by multiplying the volume of the beverage by the alcohol percentage.
Body Weight: Alcohol distributes into the water content of the body; more mass usually means more dilution.
Gender Constant (r): Men typically have a higher water percentage (approx. 68%) than women (approx. 55%), affecting the distribution ratio.
Elimination Rate (β): The body metabolizes alcohol over time. The average rate is approximately 0.015% per hour.
BAC Levels and Effects
BAC Range
Typical Effects
0.02% – 0.03%
Slight relaxation, subtle mood elevation.
0.05% – 0.06%
Feeling of warmth, relaxation, slight impairment of judgment.
0.08%
Legal limit in many regions. Impaired coordination and reaction time.
0.10% – 0.12%
Significant motor impairment, slurred speech, loss of judgment.
0.15% +
Severe intoxication, major loss of balance, potential vomiting.
Standard Drink Reference
A "standard drink" in the US contains roughly 14 grams of pure alcohol. This typically equals:
12 fl oz of regular beer (approx. 5% ABV)
5 fl oz of table wine (approx. 12% ABV)
1.5 fl oz of distilled spirits (approx. 40% ABV)
Factors That Can Influence Your Results
While the formula is accurate, real-world results can vary based on:
Food Consumption: Drinking on an empty stomach leads to faster absorption and a higher peak BAC.
Metabolic Rate: Variations in liver enzymes can speed up or slow down alcohol processing.
Medication: Certain drugs can interact with alcohol, intensifying its effects.
Body Composition: Muscle contains more water than fat, affecting how alcohol is distributed.
function calculateBAC() {
var weightLbs = parseFloat(document.getElementById('bac_weight').value);
var gender = document.getElementById('bac_gender').value;
var volumeOz = parseFloat(document.getElementById('bac_volume').value);
var abv = parseFloat(document.getElementById('bac_abv').value);
var hours = parseFloat(document.getElementById('bac_time').value);
var resultBox = document.getElementById('bac_result_box');
var outputValue = document.getElementById('bac_output_value');
var outputStatus = document.getElementById('bac_output_status');
if (isNaN(weightLbs) || isNaN(volumeOz) || isNaN(abv) || isNaN(hours) || weightLbs <= 0) {
alert("Please enter valid positive numbers for all fields.");
return;
}
// Widmark Formula constants
// r = distribution ratio (0.68 for men, 0.55 for women)
var r = (gender === 'male') ? 0.68 : 0.55;
// Alcohol consumed in grams
// 1 fl oz = 29.5735 ml
// Ethanol density = 0.789 g/ml
var alcoholGrams = volumeOz * 29.5735 * (abv / 100) * 0.789;
// Weight in grams
var weightGrams = weightLbs * 453.592;
// Theoretical BAC (ignoring time)
// BAC = [Alcohol in grams / (Weight in grams * r)] * 100
var rawBac = (alcoholGrams / (weightGrams * r)) * 100;
// Adjusted BAC for time (Metabolic rate approx 0.015% per hour)
var eliminationRate = 0.015;
var finalBac = rawBac – (hours * eliminationRate);
// Ensure BAC doesn't go below 0
if (finalBac < 0) {
finalBac = 0;
}
// Display Result
outputValue.innerHTML = finalBac.toFixed(3) + "%";
resultBox.style.display = "block";
// Set Status Color and Text
if (finalBac === 0) {
resultBox.style.backgroundColor = "#f1f2f6";
outputStatus.innerHTML = "Sober";
outputStatus.style.color = "#2f3542";
} else if (finalBac < 0.05) {
resultBox.style.backgroundColor = "#e1f5fe";
outputStatus.innerHTML = "Below Legal Limit (Safe Zone)";
outputStatus.style.color = "#0288d1";
} else if (finalBac < 0.08) {
resultBox.style.backgroundColor = "#fff9c4";
outputStatus.innerHTML = "Approaching Legal Limit (Caution)";
outputStatus.style.color = "#fbc02d";
} else if (finalBac < 0.15) {
resultBox.style.backgroundColor = "#ffebee";
outputStatus.innerHTML = "Legally Intoxicated (Do Not Drive)";
outputStatus.style.color = "#c62828";
} else {
resultBox.style.backgroundColor = "#ffcdd2";
outputStatus.innerHTML = "Dangerously High Intoxication";
outputStatus.style.color = "#b71c1c";
}
// Smooth scroll to results
resultBox.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}