PocketCalcs

BAC Calculator

Important Disclaimer: This calculator provides estimates only and should never be used to determine your ability to drive or operate machinery. BAC varies based on many factors not accounted for here. When in doubt, do not drive. Always use a designated driver or alternative transportation.
1 standard drink = 14g of pure alcohol

Frequently Asked Questions

What is Blood Alcohol Content (BAC)?

Blood Alcohol Content (BAC) is a measure of the amount of alcohol in your bloodstream, expressed as a percentage. For example:

  • 0.00% BAC means no alcohol in your system
  • 0.08% BAC is the legal limit for driving in most U.S. states
  • 0.10% BAC means 0.1 grams of alcohol per 100 mL of blood
  • BAC levels above 0.30% can be life-threatening
What is a "standard drink"?

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

  • 12 oz of regular beer (5% alcohol)
  • 5 oz of wine (12% alcohol)
  • 1.5 oz of distilled spirits/liquor (40% alcohol)
  • 8 oz of malt liquor (7% alcohol)

Many drinks served at bars and restaurants contain more than one standard drink.

How does the body metabolize alcohol?

The liver metabolizes alcohol at a relatively constant rate:

  • Average metabolism rate: 0.015-0.017% BAC per hour
  • This equals roughly one standard drink per hour
  • Nothing can speed up this process - not coffee, cold showers, or food
  • Women typically have lower body water content, leading to higher BAC from the same amount of alcohol
What factors affect BAC?

Many factors influence how alcohol affects your body:

  • Body weight: Larger people have more body water to dilute alcohol
  • Gender: Women typically have higher BAC due to differences in body composition
  • Food: Eating before or while drinking slows alcohol absorption
  • Medications: Many drugs interact with alcohol
  • Health conditions: Liver health, diabetes, and other conditions affect metabolism
  • Rate of consumption: Drinking quickly raises BAC faster
Why shouldn't I use this calculator to decide if I can drive?

This calculator provides rough estimates only and cannot account for:

  • Individual variations in alcohol metabolism
  • Food consumption and timing
  • Medications and health conditions
  • Fatigue and other impairment factors
  • Actual alcohol content of your specific drinks

Even if your calculated BAC appears low, you may still be impaired. The only safe choice is not to drive after drinking any alcohol.

What is the Widmark formula?

The Widmark formula, developed by Swedish scientist Erik Widmark in the 1930s, estimates BAC:

  • BAC = (A / (r x W)) - (bt)
  • A = Total alcohol consumed in grams
  • r = Body water constant (0.68 for males, 0.55 for females)
  • W = Body weight in grams
  • b = Metabolism rate (~0.015 per hour)
  • t = Time in hours since drinking began

While widely used, this formula provides estimates and cannot account for all individual variations.