Wondering how alcohol affects your blood alcohol content? Our free Blood Alcohol Content (BAC) Calculator uses the scientifically proven Widmark formula to estimate your BAC level based on your weight, gender, number of drinks, and time elapsed. Includes legal driving limits and estimated time to sober up.
⚠️ Important: This calculator provides an estimate only. Never drive if you have been drinking. Actual BAC varies with food intake, medication, metabolism, and health conditions. Always err on the side of caution.
Blood Alcohol Content (BAC) Calculator
1 standard drink = 12 oz beer (5%) OR 5 oz wine (12%) OR 1.5 oz spirits (40%)
The Widmark Formula for BAC
Developed by Swedish physiologist Erik Widmark in the 1920s, the Widmark formula is the scientific standard for estimating blood alcohol content. It is used by toxicologists, law enforcement, and researchers worldwide.
BAC = (Alcohol in grams ÷ (Body weight in grams × r)) × 100 − (0.015 × Hours)
- r (Widmark factor): 0.68 for men, 0.55 for women (reflects body water distribution differences)
- Standard drink: 14 grams of pure alcohol (12 oz beer, 5 oz wine, or 1.5 oz spirits)
- Elimination rate: approximately 0.015% BAC per hour (average metabolic rate)
BAC Effects Reference Chart
| BAC Level | Typical Effects | Legal Status |
|---|---|---|
| 0.01 – 0.03% | Slight relaxation, mild mood lift | Legal everywhere |
| 0.03 – 0.06% | Reduced inhibition, slight coordination loss | Legal but impaired |
| 0.06 – 0.08% | Impaired judgment and reaction time | Near legal limit — do not drive |
| 0.08%+ | Significantly impaired coordination and judgment | Illegal to drive (all US states) |
| 0.15%+ | Severe impairment, vomiting, loss of balance | Extremely dangerous |
| 0.30%+ | Risk of unconsciousness, respiratory depression | Medical emergency |
Legal BAC Limits by Country
| Country/Region | Driving Limit |
|---|---|
| USA (most states) | 0.08% |
| UK | 0.08% |
| Canada | 0.08% |
| Australia | 0.05% |
| Most of Europe | 0.05% |
| Sweden, Norway | 0.02% |
Frequently Asked Questions
How is blood alcohol content (BAC) calculated?
BAC is estimated using the Widmark formula: (Alcohol in grams ÷ (Body weight in grams × Widmark factor)) × 100, minus the elimination rate × hours elapsed. The Widmark factor is 0.68 for men and 0.55 for women. One standard US drink contains 14 grams of pure alcohol. The body metabolizes approximately 0.015% BAC per hour on average.
How long does it take for BAC to reach zero?
The body metabolizes alcohol at roughly 0.015% BAC per hour. To calculate time to sober: divide your BAC by 0.015. For example, a BAC of 0.08% takes approximately 5.3 hours to reach 0.00%. Coffee, cold showers, and food do not speed alcohol metabolism — only time does.
What is a standard drink?
In the United States, one standard drink contains 14 grams (0.6 oz) of pure alcohol. This equals: one 12 oz beer at 5% ABV, one 5 oz glass of wine at 12% ABV, or one 1.5 oz shot of 80-proof spirits (40% ABV). Many craft beers, cocktails, and wine pours contain more alcohol than a single standard drink.
Why does gender affect BAC calculation?
Women typically have a higher body fat percentage and less body water than men of the same weight. Since alcohol distributes through body water rather than fat, women achieve a higher BAC than men from the same amount of alcohol. The Widmark factor accounts for this: 0.68 for men and 0.55 for women.
How accurate is this BAC calculator?
This calculator provides a scientific estimate using the Widmark formula, which is the accepted standard for BAC estimation. However, actual BAC varies based on food consumption, drinking speed, medication interactions, individual metabolism, liver health, and genetic factors. Always treat the result as an estimate and never drive after drinking, even if your calculated BAC appears below the legal limit.