BAC Calculator

This BAC calculator estimates your blood alcohol content based on drinks consumed, your weight, gender, and time elapsed. It is for educational purposes only — the only safe BAC for driving is 0.00%.

How to Use This Calculator

1. Enter the number of drinks consumed (one standard drink = 12 oz 5% beer, 5 oz 12% wine, or 1.5 oz 40% spirits).
2. Enter your body weight.
3. Select your gender.
4. Enter the time since first drink (hours).
5. Click Calculate to see estimated BAC.

Widmark Formula

BAC = (Alcohol consumed in grams / (Body weight in grams × r)) − (Metabolism rate × hours)

• r = 0.68 (males), 0.55 (females) — body water distribution constant
• Metabolism rate = 0.015% per hour (typical; varies 0.010–0.020%)
• Standard drink ≈ 14g pure alcohol

BAC Effects Reference

• 0.02%: Mild relaxation, slight euphoria
• 0.05%: Lowered inhibitions, impaired judgment (legal to drive in most US states, but risky)
• 0.08%: Legal DUI limit in all US states — significant impairment of coordination and reaction time
• 0.15%: Severely impaired, slurred speech, loss of balance
• 0.30%: Stupor, blackout, potentially life-threatening
• 0.40%+: Risk of fatal respiratory depression

Important Disclaimers

• This is an estimate only. BAC varies with food intake, medications, fatigue, tolerance, and individual metabolism.
• The only accurate measurement is a breathalyzer or blood test by law enforcement.
• Never drive after drinking. Use a designated driver, rideshare, or taxi.
• Coffee, water, and food do not speed alcohol metabolism significantly — only time does.

Frequently Asked Questions

How long does it take to sober up?

Your liver metabolizes approximately 0.015% BAC per hour. At 0.08% BAC, you need roughly 5–6 hours to reach 0.00% — regardless of coffee, showers, or food.

Does gender affect BAC?

Yes significantly. Women typically have a lower percentage of body water (55%) compared to men (68%), so the same amount of alcohol is more concentrated in women's bloodstream. Women also have lower levels of alcohol dehydrogenase, the enzyme that metabolizes alcohol.

What factors make BAC estimates less accurate?

Food consumed (slows absorption significantly), medications (many interact with alcohol), body fat percentage (fat contains less water), individual variation in liver enzyme activity, and drink strength variation all affect actual BAC.

Conclusion

Understanding how alcohol affects your body is an important safety tool. Use this calculator to make informed decisions — and always plan ahead for a sober way home. The legal limit is a floor, not a target.

Related: Calorie Calculator | BMI Calculator