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Hndy Tools

Blood Alcohol (BAC) Calculator

Estimate your blood alcohol concentration using the Widmark formula

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Safety
Alcohol

Medical Disclaimer

This calculator provides a rough estimate only based on population averages and the Widmark formula. Actual BAC depends on many individual factors including metabolism, food intake, medications, liver function, hydration, and body composition. Never use this estimate to determine whether you are safe to drive. The only safe BAC for driving is 0.00%. If you have consumed alcohol, do not drive.

Alcohol Consumption

Drink Calculator — Convert Actual Drinks to Standard Drinks

~14g alcohol per drink

About This Tool

This Blood Alcohol Calculator uses the Widmark formula — the gold standard for forensic BAC estimation — to provide an approximate blood alcohol concentration based on your drinks, weight, sex, and time since your first drink.

  • Widmark Formula: BAC% = (grams of alcohol ÷ (body weight in grams × r)) × 100 − (β × hours). The Widmark factor (r) accounts for differing body water distribution between males (0.68) and females (0.55). The elimination rate (β = 0.015%/hr) represents average liver metabolism.
  • Standard Drinks: Each standard drink contains 14g of pure alcohol — equivalent to one 12 oz beer (5% ABV), one 5 oz glass of wine (12% ABV), or one 1.5 oz shot of spirits (40% ABV).
  • Client-Side Privacy: All calculations happen entirely in your browser. No personal data, measurements, or alcohol consumption information is ever sent to any server.

For more health and wellness tools, see our Alcohol Impact Calculator, Caffeine Half-Life Calculator, and Sleep Debt Calculator.

Frequently Asked Questions (FAQ)

What is BAC and how is the Widmark formula used?
BAC (Blood Alcohol Concentration) measures the percentage of alcohol in your bloodstream. This calculator uses the Widmark formula: BAC% = (grams of alcohol ÷ (body weight in grams × r)) × 100 − (β × hours). The Widmark factor r (0.68 for males, 0.55 for females) accounts for body water distribution differences. The elimination rate β (0.015% per hour) represents the average rate at which the liver metabolizes alcohol.
Can I use this to determine if I am safe to drive?
No. Never use this calculator to decide whether to drive. This is a rough estimate based on population averages. Your actual BAC depends on individual factors including metabolism, food intake, medications, liver function, hydration, and body composition. The only safe BAC for driving is 0.00%. If you have consumed any alcohol, do not drive — use a rideshare service, taxi, or designated driver instead.
What counts as one standard drink?
In the United States, one standard drink contains approximately 14 grams of pure alcohol. This equals 12 oz of beer (5% ABV), 5 oz of wine (12% ABV), or 1.5 oz of distilled spirits (40% ABV). Use the drink calculator section to convert actual drinks into standard drinks. Note that craft beers, fortified wines, and large pours may contain significantly more alcohol.
How does the body eliminate alcohol?
The liver metabolizes approximately 0.015% BAC per hour (about one standard drink per hour). This rate is largely constant — coffee, cold showers, food, or exercise do not speed up alcohol elimination. Time is the only thing that reduces your BAC. If your BAC is 0.08%, it will take approximately 5–6 hours to return to 0.00%. For more wellness tracking, see our Caffeine Half-Life Calculator.
What factors affect BAC beyond weight and sex?
Many individual factors influence BAC: food in the stomach slows absorption; body composition (muscle vs. fat) affects distribution; medications can interact with alcohol metabolism; liver health determines elimination rate; carbonation in drinks speeds absorption; and genetics affect enzyme efficiency. This is why BAC estimates should never be relied upon for safety decisions. Track your overall health with our Sleep Debt Calculator.
What do the different legal limits mean?
Many countries (including most of Europe, Australia, and South America) set the legal driving limit at 0.05% BAC. The United States uses 0.08% BAC. Some countries (e.g., Sweden, Norway) have even lower limits of 0.02%. Commercial drivers often face stricter limits. For alcohol-related health impact assessments, try our Alcohol Impact Calculator.

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