BAC Calculator

1 standard drink = 12 oz beer / 5 oz wine / 1.5 oz spirits

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Estimate only. Never drive based on a calculator result. If in doubt, don't drive.

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The Widmark Formula

BAC% = (A × 100) / (W × r) − 0.015 × H
A = alcohol in grams (drinks × 14)
W = body weight in grams
r = 0.68 (male) or 0.55 (female) — Widmark factor
H = hours elapsed since first drink

BAC Impairment Levels

< 0.02% Little to no effect for most people
0.02–0.05% Mild relaxation, slight mood change, minor impairment
0.05–0.08% Noticeable impairment: judgment, reaction time, coordination
0.08% Legal driving limit in all US states
0.08–0.15% Significant impairment, slurred speech, balance issues
0.15–0.25% Severe impairment, possible blackout
0.25%+ Life-threatening — risk of loss of consciousness

Tips

  • Food slows alcohol absorption significantly. Eating a meal before or while drinking lowers peak BAC and delays impairment.
  • Many cocktails and craft beers contain 1.5–2+ standard drinks. Check the ABV and portion size, not just the number of glasses.
  • Coffee, water, and time are the only things that reduce BAC. Only time eliminates alcohol from your system.

Frequently Asked Questions

What is a standard drink?

In the US, one standard drink contains 14 grams of pure alcohol. This equals approximately: 12 oz regular beer (5% ABV), 5 oz wine (12% ABV), or 1.5 oz distilled spirits (40% ABV/80 proof). Many craft beers, cocktails, and glasses of wine contain more than one standard drink.

How accurate is this calculator?

This is an estimate only, not a breathalyzer substitute. Actual BAC varies based on food intake, hydration, medications, tolerance, individual metabolism, and the exact alcohol content of your drinks. Never rely on a calculator to determine if it's safe to drive.

What is the legal BAC limit for driving?

In the United States, the legal limit for driving is 0.08% BAC for adults 21 and over in all 50 states. Commercial drivers face a lower limit of 0.04%. Drivers under 21 are subject to zero-tolerance laws (0.00–0.02% depending on state).

How long does it take for BAC to return to zero?

The liver metabolizes alcohol at a rate of approximately 0.015% BAC per hour — one standard drink per hour for most adults. This rate is relatively constant and cannot be accelerated by coffee, water, food, or exercise after drinking.

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