How is BAC calculated?

Using the Widmark formula: BAC = (A × 5.14 / W × r) − 0.015 × H, where A = ounces of alcohol consumed, W = weight in lbs, r = 0.73 for men or 0.66 for women (distribution ratio), H = hours since drinking began.

What BAC level is legally drunk?

In the United States, the legal limit for driving is 0.08% BAC. Commercial drivers face a stricter 0.04% limit. Some states have zero-tolerance laws (0.00–0.02%) for drivers under 21. Many other countries use 0.05%.

How long does it take to sober up?

The liver processes alcohol at roughly 0.015% BAC per hour, regardless of coffee, food, or cold showers. A person with BAC 0.08% needs about 5.3 hours to reach 0.00%. There is no way to speed up this process.

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BAC Calculator

Estimate your Blood Alcohol Content (BAC) using the Widmark formula. Enter your weight, gender, drinks consumed, and hours since drinking started.

Important Safety Warning

This calculator is for informational purposes only. BAC estimates are approximate and vary based on individual metabolism, food intake, medications, and other factors. Never drink and drive. The legal limit in most US states is 0.08% BAC.

Calculate BAC

Based on the Widmark formula (1 standard drink = 0.6 oz pure alcohol)

Biological Sex

Body Weight (lbs)

Number of Standard Drinks

1 standard drink = 12 oz beer (5%), 5 oz wine (12%), or 1.5 oz spirits (40%)

Hours Since Drinking Started

BAC Effects Reference

BAC Range	Effects
0.00–0.03	Subtle effects only — legal to drive
0.04–0.06	Mild euphoria and relaxation
0.07–0.09	Impaired judgment — at or near legal limit (0.08)
0.10–0.12	Significant impairment of coordination
0.13–0.15	Gross impairment, blackout risk
0.16+	Dangerous — medical emergency risk

About BAC Calculation

Blood Alcohol Content (BAC) is a measure of the concentration of alcohol in the bloodstream, expressed as a percentage. The Widmark formula, developed by Swedish physician Erik Widmark in the 1920s, remains the most widely used method for BAC estimation. It accounts for body weight, biological sex (men have higher body water content, represented by the Widmark factor r = 0.73 vs. 0.66 for women), total alcohol consumed, and the body's natural elimination rate of approximately 0.015% per hour.

BAC is influenced by many factors beyond what this calculator considers: food consumption (which slows alcohol absorption), drink strength, drinking speed, individual liver efficiency, medications, and hydration status. As a result, calculated BAC should never be used to determine whether it is safe to drive — only a certified breathalyzer or blood test can do that. Many people feel impaired well before reaching the 0.08% legal limit. If you're focused on overall wellness, our Sleep Calculator and Calorie Calculator provide additional health insights.

This calculator is for informational purposes only and does not constitute legal or medical advice. Never drink and drive. If you or someone you know needs support with alcohol use, contact the SAMHSA National Helpline at 1-800-662-4357 (free, confidential, 24/7).

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Take this calculation further

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For a related calculation, use Sleep Calculator to calculate ideal bedtimes or wake times based on 90-minute sleep cycles for optimal rest. Alternatively, use Target Heart Rate Calculator to calculate target heart rate zones using the Karvonen method for optimal training intensity.

For the underlying method, read How to Calculate Your Ideal Race Pace for Any Distance or Why Sleep Cycles Matter More Than Sleep Duration.