BAC Calculator

Welcome to the BAC Calculator (Blood Alcohol Content Calculator), a tool that estimates your current BAC based on the number and type of alcoholic drinks consumed, your body weight, biological sex, and time elapsed since your first drink. The calculator uses the Widmark formula, the most widely accepted scientific method for estimating blood alcohol concentration.

What Is Blood Alcohol Content (BAC)?

Blood Alcohol Content (also called Blood Alcohol Concentration or Blood Alcohol Level) measures the percentage of alcohol in your bloodstream. It is expressed as a decimal — for example, a BAC of 0.08% means 0.08 grams of alcohol per 100 milliliters of blood. BAC is the standard metric used by law enforcement, medical professionals, and researchers worldwide to quantify alcohol intoxication.

How the Widmark Formula Works

This calculator uses the Widmark formula, developed by Swedish physician Erik Widmark in the 1930s and still the standard for BAC estimation:

BAC = (Alcohol consumed in oz × 5.14) ÷ (Body weight in lbs × r) − (0.015 × Hours)

Where r is the Widmark factor (0.73 for males, 0.66 for females), reflecting differences in body water distribution. The constant 0.015 represents the average hourly alcohol elimination rate.

What Is a Standard Drink?

In the United States, one standard drink contains approximately 14 grams (0.6 ounces) of pure alcohol. This is equivalent to:

• Beer: 12 oz at 5% ABV
• Wine: 5 oz at 12% ABV
• Spirits/Liquor: 1.5 oz (one shot) at 40% ABV
• Cocktails: Vary widely, typically 1 to 2 standard drinks each

BAC Levels and Their Effects

Legal BAC Limits Around the World

• United States: 0.08% (Utah: 0.05%), 0.04% for commercial drivers
• United Kingdom: 0.08% (England, Wales), 0.05% (Scotland)
• Australia: 0.05%
• Germany / France / Spain: 0.05%
• Japan / Sweden / Poland: 0.03%
• Brazil / Czech Republic / Hungary: 0.00% (zero tolerance)

Factors That Affect BAC

• Body weight: Higher body weight generally means lower BAC for the same number of drinks
• Biological sex: Women typically reach higher BAC than men at the same weight due to differences in body water percentage and metabolism
• Rate of consumption: Drinking faster leads to higher peak BAC
• Food intake: Eating before or while drinking slows alcohol absorption
• Medications: Many medications can intensify alcohol effects
• Liver health: Liver conditions can slow alcohol metabolism
• Tolerance: Tolerance affects perceived impairment but does NOT change BAC

How to Use This Calculator

1. Enter your drinks: Use the drink counter to select how many beers, wines, shots, or cocktails you consumed. Use + and - buttons to adjust.
2. Enter body information: Provide your body weight (in pounds or kilograms) and select your biological sex.
3. Enter time elapsed: Enter hours since you started drinking. This accounts for alcohol your body has already metabolized.
4. View results: See your estimated BAC, impairment level, time until sober, and a detailed decline timeline.

Myths About Sobering Up

• Coffee does NOT lower BAC — caffeine may make you feel more alert, but your BAC and impairment remain the same
• Cold showers do NOT help — they may wake you up, but alcohol is still in your system
• Eating after drinking does NOT reduce BAC — food only slows absorption if consumed before or during drinking
• Exercise does NOT speed up metabolism — only time allows your liver to process alcohol
• Only time works — the body eliminates alcohol at about 0.015 BAC per hour, and nothing can accelerate this

Frequently Asked Questions

What is Blood Alcohol Content (BAC)?

Blood Alcohol Content (BAC) is a measurement of the amount of alcohol in your bloodstream, expressed as a percentage. A BAC of 0.08% means there are 0.08 grams of alcohol per 100 milliliters of blood. BAC is influenced by the amount of alcohol consumed, body weight, biological sex, and time elapsed since drinking.

What is a standard drink?

In the United States, a standard drink contains about 14 grams (0.6 ounces) of pure alcohol. This equals approximately one 12-oz beer at 5% ABV, one 5-oz glass of wine at 12% ABV, or one 1.5-oz shot of distilled spirits at 40% ABV. Cocktails typically contain 1 to 2 standard drinks depending on the recipe.

What is the legal BAC limit for driving?

In 49 US states and the District of Columbia, the legal BAC limit for drivers aged 21 and over is 0.08%; Utah lowered its limit to 0.05% at the end of 2018. For commercial drivers, the limit is typically 0.04%. Most states have zero-tolerance laws for drivers under 21, with limits of 0.00% to 0.02%. Many other countries have lower limits, such as 0.05% in Australia and most of Europe.

How long does it take for BAC to reach zero?

The body eliminates alcohol at an average rate of about 0.015 BAC per hour (roughly one standard drink per hour). This rate is fairly constant regardless of body size or gender. For example, a BAC of 0.08% would take approximately 5 hours and 20 minutes to reach zero. Only time can lower your BAC — coffee, cold showers, and food do not speed up alcohol metabolism.

How accurate is a BAC calculator?

BAC calculators provide estimates based on the Widmark formula and population averages. Individual results can vary significantly based on factors like metabolism, food intake, medications, liver health, body composition, and rate of consumption. These calculators should never be used to determine if you are safe to drive. When in doubt, do not drive.