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Blood Alcohol Content (BAC) Calculator

Estimate your blood alcohol concentration (BAC) using our research-backed calculator. Based on number of drinks, gender, weight, and hours since drinking began.

Medical Disclaimer: This tool provides general educational estimates. Always consult your prescribing physician or healthcare provider before making medication changes or interpreting results from population-based models.

Contents

Used for body water distribution differences
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How This BAC Calculator Works

Understanding BAC

Blood Alcohol Content (BAC) is a measure of alcohol in the bloodstream expressed as a percentage. For example, a BAC of 0.08% means that 0.08% of your blood is alcohol.

How We Calculate BAC

This calculator uses the Widmark formula, which is widely accepted for BAC estimation:

BAC = (Alcohol consumed in grams / (Body weight in kg × r)) - (0.015 × Hours)

Where:

  • r is the gender-specific distribution ratio (0.68 for men, 0.55 for women)
  • 0.015 is the average alcohol elimination rate per hour

How to Use the Calculator

  1. Select your preferred unit system (metric or imperial)
  2. Enter your gender and body weight
  3. Specify how many hours have passed since your first drink
  4. Add the drinks you've consumed, specifying:
    • The type of drink
    • The alcohol percentage
    • The volume consumed
  5. Click "Calculate BAC" to see your results

Understanding the Results

The calculator provides:

  • Your estimated BAC percentage
  • The corresponding impairment level
  • Estimated time until you're completely sober (0.00% BAC)
  • Estimated time until you're below the legal limit (0.08% BAC)

Important Safety Warning

This calculator provides an estimate only and should never be used to determine if you're safe to drive or operate machinery. Even small amounts of alcohol can impair judgment and reaction time.

If you've been drinking, arrange for alternative transportation or wait until you're completely sober.

📘 Related Guide

Want to understand how your body absorbs and eliminates alcohol? Read the full BAC Absorption Guide →

📘 Related Tool

Want to understand how drinking affects more than just your BAC? Our Alcohol Impact Calculator analyzes sleep quality, hydration loss, liver stress, and long-term health impacts of your drinking patterns. Try the Alcohol Impact Calculator →

Frequently Asked Questions

What factors affect BAC calculations?

While our calculator accounts for key variables, these additional factors can influence actual BAC:

  • Individual metabolism variations
  • Medications
  • Liver function
  • Genetics
  • Hydration level

For accurate BAC measurement, use a certified breathalyzer or blood test.

What is the legal BAC limit for driving?

Legal limits vary by jurisdiction:

  • 0.08% - Most U.S. states and many countries
  • 0.05% - Australia, France, Germany, Italy
  • 0.02-0.03% - Sweden, Poland, Norway
  • 0.00% - Hungary, Romania, Slovakia (zero tolerance)

Some regions have lower limits (often 0.04%) for commercial drivers and zero tolerance policies for drivers under 21.

How long does alcohol stay in your system?

On average, the body metabolizes alcohol at a rate of about 0.015% BAC per hour. For example, if your BAC is 0.08%, it would take approximately 5.3 hours to return to 0.00%.

However, alcohol can be detected in:

  • Breath: 12-24 hours
  • Blood: Up to 12 hours
  • Urine: 12-48 hours (up to 80 hours with advanced testing)
  • Hair: Up to 90 days

What are the symptoms of different BAC levels?

BAC levels typically correlate with these symptoms:

  • 0.02-0.03%: Slight euphoria, relaxation, mild impairment of reasoning
  • 0.04-0.06%: Feeling of warmth, relaxation, minor impairment of memory and judgment
  • 0.07-0.09%: Slight speech impairment, balance issues, decreased reaction time (legally intoxicated in most places)
  • 0.10-0.12%: Significant impairment of motor coordination, slurred speech, poor judgment
  • 0.13-0.15%: Major loss of physical control, blurred vision, major loss of balance
  • 0.16-0.20%: Dysphoria, nausea, appearance of "sloppy drunk"
  • 0.25%: Severe intoxication, mental confusion, need for assistance moving
  • 0.30%: Possible unconsciousness, minimal comprehension
  • 0.35%+: Surgical anesthesia, potential death (0.40%+)

Can coffee, cold showers, or food help lower BAC?

No. These common myths cannot accelerate alcohol metabolism. The only effective factor is time.

While food in your stomach before drinking can slow alcohol absorption (reducing peak BAC), once alcohol is in your bloodstream, only your liver can metabolize it at a relatively fixed rate (about 0.015% per hour).

Coffee may make you feel more alert but doesn't reduce BAC. Cold showers might make you feel more awake but don't affect BAC. These methods can be dangerous by giving a false sense of sobriety.

Why does gender affect BAC calculations?

Gender is included in BAC calculations due to physiological differences:

  1. Body composition: Biological males typically have a higher percentage of water in their bodies (about 58% vs. 49% in females), which dilutes alcohol more effectively
  2. Enzyme differences: Males generally have more alcohol dehydrogenase (the enzyme that breaks down alcohol) in their stomachs

These differences mean that, on average, a female drinking the same amount of alcohol as a male of identical weight will have a higher BAC.