BAC Calculator

Estimate your Blood Alcohol Content based on what you've had to drink, your weight, and time. Educational tool — never drink and drive.

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Important Disclaimer

This calculator provides an educational estimate only. Individual BAC varies based on metabolism, food intake, medications, health conditions, and other factors. Never drink and drive. If in doubt, don't drive.

1 standard drink = 0.6 fl oz (14g) of pure alcohol (approx. 12oz beer, 5oz wine, 1.5oz spirits)

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Beer (12oz)

0
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Wine (5oz)

0
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Shot (1.5oz)

0
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Cocktail

0
Total standard drinks: 0
2 hrs

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About This BAC Calculator

This calculator uses a simplified Widmark formula to estimate Blood Alcohol Content. It's intended for educational purposes only and should not be used to determine whether you are safe to drive or operate machinery.

How BAC Is Calculated

The basic Widmark formula:

BAC = (Alcohol in Grams ÷ (Body Weight in Grams × R)) × 100 - (Elimination Rate × Hours)

Where:

  • R (Widmark factor): ~0.68 for men, ~0.55 for women (water distribution ratio)
  • Elimination rate: ~0.015% per hour (average; varies by individual)
  • 1 standard drink: ~14 grams (0.6 fl oz) of pure alcohol

Standard Drink Sizes

Not all drinks contain the same amount of alcohol. A "standard drink" contains about 0.6 fluid ounces (14 grams) of pure alcohol:

  • Beer: 12 fl oz (5% ABV)
  • Wine: 5 fl oz (12% ABV)
  • Distilled spirits: 1.5 fl oz (40% ABV / 80 proof)
  • Malt liquor: 8-9 fl oz (7% ABV)
  • Fortified wine (sherry, port): 3-4 fl oz (17% ABV)

Factors That Affect BAC

Body Weight & Composition

Heavier people have more body water, which dilutes alcohol more, resulting in lower BAC for the same number of drinks. Muscle tissue contains more water than fat tissue.

Sex

Women typically have a higher percentage of body fat and lower body water than men of the same weight. Women also generally have lower levels of alcohol dehydrogenase (the enzyme that breaks down alcohol).

Food

Drinking on an empty stomach results in faster absorption and higher peak BAC. Food — especially high-protein, high-fat meals — slows alcohol absorption significantly.

Rate of Consumption

The faster you drink, the higher your BAC rises. The liver can only metabolize about one standard drink per hour. Drinking faster than that causes BAC to climb.

Legal BAC Limits in the US

  • Drivers 21+: 0.08% BAC (all 50 states)
  • Drivers under 21: 0.00-0.02% (zero tolerance laws vary by state)
  • Commercial drivers: 0.04% BAC

Even at BAC levels below 0.08%, driving ability is impaired. The safest choice is always: if you drink, don't drive.

Warning Signs of Alcohol Poisoning

If someone has been drinking heavily and shows these signs, call 911 immediately:

  • Confusion or inability to wake up
  • Vomiting while passed out
  • Seizures
  • Slow or irregular breathing (fewer than 8 breaths per minute)
  • Pale or blue-tinged skin
  • Low body temperature (hypothermia)

Don't leave an intoxicated person alone to "sleep it off." Alcohol poisoning can be fatal. Stay with them and call for help.