Blood Alcohol Calculator
Estimated BAC and hours until sober.
Enter your values
Results update instantly as you type — no submit needed.
Results
- Estimated BAC
- 0.05%
- Legal to drive in the US (0.08)
- Under the limit — but impairment starts far lower
- Hours until zero
- 3.3 hours
- Peak BAC before metabolism
- 0.08%
Quick answer
The Widmark formula estimates BAC as alcohol grams ÷ (body weight × distribution factor), minus about 0.015% per hour of metabolism.
BAC = (grams alcohol ÷ (kg × r)) × 100 − 0.015 × hours
How to use the Blood Alcohol Calculator
- 1Count your standard drinks (14 g alcohol each).
- 2Enter body weight and hours elapsed.
- 3Read the estimated BAC.
Frequently asked questions
Is this safe to rely on for driving?
No. Individual variation is large, and impairment begins below any legal limit. Never use an estimate to decide whether to drive.
What is a standard drink?
12 oz of 5% beer, 5 oz of 12% wine or 1.5 oz of 40% spirits — each contains about 14 g of pure alcohol.