About Blood Alcohol Level Calculator

What This Calculator Does

Blood Alcohol Level Calculator is a free online tool that estimates your blood alcohol content (BAC) based on several personal factors. The calculator includes four specialized tools, each designed for different scenarios:

BAC Calculator — The primary tool estimates your current blood alcohol content based on your gender, body weight, the number and type of drinks consumed, and how much time has passed since you started drinking. It displays your estimated BAC percentage, the likely effects at that level, total alcohol consumed in grams, and how long until you reach both the legal limit (0.08%) and complete sobriety (0.00%).

Time to Sober Calculator — This tool calculates how long you need to wait before reaching a target BAC level. Enter your current BAC (measured or estimated) and select your target level—whether completely sober, minimal impairment, or the legal limit. The calculator shows the hours needed and the approximate clock time when you'll reach your target.

BAC Chart — A reference table showing estimated BAC levels for different body weights (100-240 lbs) across 1-6 standard drinks. The chart uses color coding—green for safe, yellow for caution, and red for over the legal limit—making it easy to quickly reference approximate BAC levels without entering individual calculations.

Drinks to BAC Calculator — This reverse calculator determines approximately how many drinks would bring you to a specific BAC level. Enter your gender, weight, target BAC, and the time period over which you'd be drinking. The tool shows the number of standard drinks and equivalent amounts in beer, wine, and spirits.

The Science Behind It

Our calculator uses the Widmark formula, the most widely accepted method for estimating blood alcohol content. Developed by Swedish scientist Erik Widmark in the 1930s, this formula remains the standard in forensic toxicology and is used by law enforcement, medical professionals, and researchers worldwide.

The core formula is:

BAC = (Alcohol in grams / (Body weight in grams × r)) × 100

Where r is the Widmark factor (also called the distribution ratio), which accounts for how alcohol distributes through body water. This calculator uses r = 0.68 for men and r = 0.55 for women, values derived from population studies and commonly used in forensic applications.

Alcohol content calculation: The calculator determines alcohol in grams using the formula: Volume (ml) × ABV (decimal) × 0.789, where 0.789 g/ml is the density of ethanol. A standard drink contains approximately 14 grams of pure alcohol.

Metabolism adjustment: The human body eliminates alcohol at a relatively constant rate of approximately 0.015% BAC per hour (range: 0.010-0.020%). This calculator uses the 0.015% average and subtracts the metabolized alcohol from the gross BAC calculation based on hours elapsed since drinking began.

Standard drink definitions used in calculations:

  • Beer: 12 oz (355 ml) at 5% ABV = 14g alcohol
  • Wine: 5 oz (148 ml) at 12% ABV = 14g alcohol
  • Spirits: 1.5 oz (44 ml) at 40% ABV = 14g alcohol

Who This Is For

This calculator serves anyone who wants to better understand how alcohol affects their body. Common use cases include:

Educational purposes — Students, educators, and curious individuals learning about alcohol metabolism, the Widmark formula, and how factors like weight and gender affect BAC.

Planning and awareness — People who want to understand roughly how different drinking scenarios might affect their BAC over time. This can inform decisions about transportation, timing, and consumption levels before social events.

General reference — Anyone seeking a quick reference for standard drink equivalents, BAC levels by weight, or the relationship between drinks consumed and estimated impairment.

Health-conscious individuals — Those monitoring their alcohol intake as part of broader health and wellness goals who want to understand consumption in concrete terms.

This calculator is not intended as a tool to determine if you are "safe" to drive. No calculator can account for all individual factors, and the only safe choice after drinking is to avoid driving entirely.

Our Methodology

The calculations in this tool follow established scientific consensus on alcohol pharmacokinetics:

Gender-based distribution ratios — Women typically have a higher percentage of body fat and lower percentage of body water compared to men of the same weight. Since alcohol is water-soluble and distributes through body water, women generally achieve higher BAC levels than men when consuming the same amount of alcohol relative to body weight. The Widmark factors (0.68 for men, 0.55 for women) are population averages that account for this difference.

Linear metabolism assumption — At typical drinking levels, alcohol metabolism follows zero-order kinetics, meaning the body eliminates a constant amount per hour regardless of the total present. The 0.015% per hour rate represents a well-established average, though individual rates can vary from 0.010% to 0.020% based on genetics, liver health, and other factors.

Instantaneous absorption model — For simplicity, this calculator assumes consumed alcohol is fully absorbed. In reality, absorption occurs over 30-90 minutes depending on stomach contents and other factors. This assumption may slightly overestimate BAC for recent consumption and underestimate peak BAC that hasn't yet been reached.

Standard drink standardization — The 14-gram standard drink used here matches the definition established by the National Institute on Alcohol Abuse and Alcoholism (NIAAA) and allows consistent comparison across beverage types.

Limitations and Disclaimer

This calculator provides estimates only. Actual blood alcohol content can vary significantly from calculated values due to numerous individual factors that no formula can fully account for:

  • Food consumption — Eating before or while drinking slows alcohol absorption and can significantly affect BAC
  • Drinking rate — The calculator assumes even distribution over the time period; rapid consumption causes higher peak BAC
  • Individual metabolism — Genetic factors, liver health, age, and medications can cause metabolism rates to vary significantly from the 0.015% average
  • Body composition — The gender-based Widmark factors are population averages; individual body composition varies
  • Drink strength — Actual alcohol content in drinks varies; craft beers, wine, and mixed drinks often exceed standard assumptions
  • Health conditions — Various medical conditions and medications can affect alcohol absorption and metabolism

Never use this calculator to decide whether you are safe to drive. Even low BAC levels can impair driving ability, and individual impairment varies. The only safe choice is to not drive after drinking any amount of alcohol. Always arrange alternative transportation—designated driver, rideshare, taxi, or public transit—when alcohol will be consumed.

This tool is for educational and informational purposes only. It does not constitute medical, legal, or professional advice. For questions about alcohol's effects on your health, consult a qualified healthcare provider. For legal questions regarding BAC and driving, consult with legal professionals in your jurisdiction.

How to Use the Calculator

BAC Calculator Tab

  1. Select your gender (this affects the Widmark distribution factor)
  2. Enter your body weight and select the unit (lbs or kg)
  3. Enter the number of drinks consumed (decimals like 1.5 are accepted)
  4. Select your drink type from the dropdown (beer, wine, spirits, or cocktail)
  5. Enter hours since your first drink
  6. Click "Calculate BAC" to see your estimated blood alcohol content, effects, and time until sober

Time to Sober Tab

  1. Enter your current BAC (either measured with a breathalyzer or estimated from the BAC Calculator)
  2. Select your target BAC from the dropdown (0.00% for completely sober, 0.08% for legal limit, etc.)
  3. Click "Calculate Time to Sober" to see hours needed and the approximate time you'll reach your target

BAC Chart Tab

No input required. The chart displays estimated BAC levels for male drinkers across different weights and drink counts. Find your approximate weight in the left column, then read across to see estimated BAC for 1-6 drinks. Color coding indicates safety levels. Note: women should expect approximately 20-25% higher BAC for the same weight and consumption.

Drinks to BAC Tab

  1. Select your gender
  2. Enter your body weight and unit
  3. Enter your target BAC percentage (e.g., 0.08 for the legal limit)
  4. Enter the time period in hours over which you'd be drinking
  5. Click "Calculate Drinks" to see how many standard drinks would reach that BAC level

Why We Built This

We created Blood Alcohol Level Calculator to provide a straightforward, accessible tool for understanding blood alcohol content without the barriers common to many online calculators:

Completely free — All calculator features are available at no cost, with no premium tiers or paywalled functionality.

No signup required — Use the calculator immediately without creating an account, providing an email address, or completing any registration process.

Privacy-focused — All calculations happen entirely in your web browser using JavaScript. No data about your inputs, results, or usage is transmitted to any server. Your weight, drinking information, and calculated BAC never leave your device.

No data stored — We don't use cookies to track your calculations, don't store your inputs in any database, and don't build profiles based on your usage. Each visit is independent and private.

No ads or distractions — The calculator is designed for clarity and usability, not to maximize ad impressions or keep you clicking through pages.

Our goal is simple: provide a useful, scientifically-grounded educational tool that helps people better understand alcohol's effects on the body—while being absolutely clear that no calculator should ever be used to make driving decisions after drinking.