Blood Alcohol Content (BAC) Calculator
Estimate your blood alcohol content using the Widmark formula based on drinks consumed, body weight, and time elapsed.
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% BAC
This is an estimate only. Do not use this to decide whether to drive.
What is Blood Alcohol Content (BAC) Calculator?
The Blood Alcohol Content (BAC) calculator estimates the concentration of alcohol in your bloodstream using the Widmark formula. BAC is expressed as grams of alcohol per 100 mL of blood. This calculator is for educational purposes only and should never be used to decide whether it is safe to drive.
How to use
- 1 Select your gender.
- 2 Enter your body weight and choose kg or lbs.
- 3 Enter the number of standard drinks consumed (one standard drink = 14 g of pure alcohol in the US).
- 4 Enter the number of hours since you started drinking.
- 5 Your estimated BAC appears instantly.
Formula
Example calculation
A 70 kg (154 lb) man who drinks 3 standard drinks over 2 hours: BAC = (3 × 14) / (70000 × 0.68) − 0.015 × 2 = 42/47600 − 0.03 ≈ 0.058%. Below the legal limit, but judgment is still impaired.
Frequently asked questions
What is a standard drink?
In the US, one standard drink contains 14 g of pure alcohol — roughly a 12 oz regular beer (5%), 5 oz wine (12%), or 1.5 oz distilled spirits (40%).
At what BAC is driving illegal?
In the US, Canada, and most of Europe, the legal limit for driving is 0.08% BAC. Some countries use 0.05%. Commercial drivers often face stricter limits of 0.04%.
How long does it take to sober up?
The body metabolizes alcohol at roughly 0.015% BAC per hour. At 0.08% BAC you need over 5 hours to reach zero. Coffee and cold showers do not speed this up.
Is this calculator accurate?
The Widmark formula provides an estimate. Actual BAC varies based on food intake, hydration, medications, liver health, and individual metabolism. Never rely on a calculator to judge fitness to drive.
Why does gender affect BAC?
Women generally have a lower body water ratio (r = 0.55 vs 0.68 for men), which means the same amount of alcohol is more concentrated in a woman's bloodstream.