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BAC Calculator

Q: How is BAC calculated?

This calculator uses the Widmark formula: BAC = (alcohol grams / (body weight × r)) × 100 - (0.015 × hours). Where r is 0.68 for males and 0.55 for females.

Estimate your blood alcohol content (BAC) based on the number of drinks, body weight, sex, and time elapsed. Uses the Widmark formula.

⚠ Safety: This is an estimate only. BAC varies significantly due to individual factors. If you have consumed any alcohol, do not drive. Never rely on a calculator to determine fitness to drive.

Privacy: All calculations run locally in your browser. We do not send your inputs to any server.

FAQ

How is BAC calculated?

This calculator uses the Widmark formula: BAC = (alcohol in grams / (body weight in grams × r)) × 100 − (0.015 × hours). The Widmark r factor is 0.68 for males and 0.55 for females, reflecting differences in body water content.

What is a standard drink?

In the US, a standard drink contains about 14 grams (0.6 oz) of pure alcohol. This equals approximately 12 oz of regular beer (5% ABV), 5 oz of wine (12% ABV), or 1.5 oz of distilled spirits (40% ABV).

How long does it take to sober up?

The body typically metabolizes alcohol at about 0.015% BAC per hour. Nothing speeds this up—not coffee, cold showers, or food. Only time reduces BAC.

Is this calculator accurate?

This is an approximation. Actual BAC varies by ±20% or more due to metabolism, medications, food intake, body composition, and other individual factors. Never use any BAC calculator to determine fitness to drive.