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Blood Alcohol Calculator

Estimate Blood Alcohol Content (BAC).

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Estimated BAC
Legal Status (USA)Impaired / Buzzed

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Assumptions

  • Each standard drink is treated as about 14 grams of pure alcohol.
  • The estimate uses fixed body-water distribution ratios by sex and a typical elimination rate of 0.015% BAC per hour.
  • Real BAC can vary significantly based on food intake, medications, metabolism, and drink strength.

Sensitivity preview

Body Weight -10%: Estimated BAC 0.05%

Body Weight Current: Estimated BAC 0.05%

Body Weight +10%: Estimated BAC 0.04%

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About this BAC Calculator

Blood Alcohol Content (BAC) is the percentage of alcohol in your bloodstream. This calculator estimates your BAC level to help you understand how alcohol affects your body. However, metabolism varies widely between individuals.

Who this calculator is for

  • Adults who want a rough estimate of how alcohol intake may affect impairment.
  • People comparing how drinks, body weight, and elapsed time influence BAC.
  • Anyone learning why a small number of drinks can affect people differently.

When to use it

  • Use this calculator after drinking to understand approximate BAC trends over time.
  • Use it to compare different drink counts before or after social events.
  • Use it for education about alcohol metabolism, not for legal or safety decisions.

How to use this calculator

  1. Select your Gender (affects water distribution in body).
  2. Enter your Weight.
  3. Enter the number of Standard Drinks consumed.
  4. Enter Hours since your first drink.
  5. The result is your estimated % BAC.

Key assumptions

  • Each standard drink is treated as about 14 grams of pure alcohol.
  • The estimate uses fixed body-water distribution ratios by sex and a typical elimination rate of 0.015% BAC per hour.
  • Real BAC can vary significantly based on food intake, medications, metabolism, and drink strength.

Accuracy and testing

Review formula sources, default test cases, assumptions, unit handling, rounding rules, and changelog for this calculator.

View accuracy page

How this calculator works

This calculator uses the Widmark Formula: `BAC = [Alcohol(g) / (Body Weight(g) × r)] × 100 - (0.015 × Hours)` * r (distribution ratio): 0.68 for men, 0.55 for women. * Metabolism: Assumes body eliminates alcohol at 0.015% per hour.

Inputs explained

Standard Drink

12 oz beer (5%), 5 oz wine (12%), or 1.5 oz spirits (40%). Each contains ~14 grams of pure alcohol.

Hours

Time elapsed since you started drinking. Time is the only thing that lowers BAC.

Understanding your results

In the US, the legal limit for driving is 0.08%. * 0.02-0.03%: Mild relaxation. * 0.05-0.07%: Buzz, lowered inhibitions. * 0.08%+: Impaired motor skills, illegal to drive. * 0.20%+: Severe impairment, blackout risk.

Example scenarios

Male Example

180 lbs, 3 beers, 2 hours. BAC ≈ 0.03%. (Safe range).

Female Example

130 lbs, 3 glasses wine, 2 hours. BAC ≈ 0.08%. (Legal limit).

Key Features

  • Widmark Formula
  • Time Decay Factor
  • Legal Status Check

Things to Keep in Mind

Strictly an estimate. Actual BAC depends on genetics, body composition, food intake, and medications. **Do not use this tool to decide if you can drive.**

Tips & Best Practices

  • Food slows absorption but does not prevent intoxication.
  • Coffee and cold showers do not lower BAC; only time does.
  • Tolerance does not change your BAC, only how 'sober' you feel.

Glossary of Terms

Widmark Formula
The most widely used theoretical method for estimating BAC.
Metabolic Rate
The rate at which the liver processes alcohol (avg 0.015% BAC per hour).

Frequently Asked Questions

How fast does BAC drop?
On average, BAC drops by 0.015% per hour. It takes about one hour to metabolize one standard drink.
Does eating lower BAC?
Eating *before* drinking slows the absorption of alcohol into the bloodstream, keeping peak BAC lower. Eating *after* drinking does not lower BAC.
Is this admissible in court?
No. Only a certified breathalyzer or blood test administered by law enforcement or medical professionals is accurate enough for legal purposes.
Why does gender matter?
Women generally have less body water and less of the enzyme dehydrogenase than men, leading to a higher BAC for the same amount of alcohol.