BAC Calculator
Estimate your Blood Alcohol Content based on drinks consumed, body weight, and time elapsed.
Sober 0.05%
Buzzed 0.08%
Legal Limit 0.15%
Impaired 0.30%+
Danger
How BAC is Calculated
BAC is calculated using the Widmark formula, which accounts for the amount of alcohol consumed, body weight, gender (men and women metabolize alcohol differently), and time elapsed.
One “standard drink” in the US contains about 14 grams of pure alcohol: 12oz beer (5%), 5oz wine (12%), or 1.5oz spirits (40%). Your body metabolizes alcohol at approximately 0.015% per hour.
Understanding BAC Levels
- 0.02-0.03%: Slight mood elevation, relaxation. Minimal impairment.
- 0.05-0.06%: Lowered inhibitions, minor impairment of reasoning and memory.
- 0.08-0.10%: Legal intoxication in most states. Impaired balance, speech, reaction time.
- 0.15-0.20%: Major impairment. Difficulty walking, blurred vision, slurred speech.
- 0.30%+: Medical emergency risk. Loss of consciousness possible.
Factors Affecting BAC
- Body weight: Higher weight generally means lower BAC from same amount of alcohol.
- Gender: Women typically have higher BAC due to different body composition and enzymes.
- Food intake: Eating before or while drinking slows alcohol absorption significantly.
- Drink rate: Faster drinking leads to higher peak BAC before metabolism catches up.
Important Safety Information
- Never drive impaired: Even below 0.08%, alcohol impairs judgment and reaction time.
- Plan ahead: Designate a sober driver, use rideshare, or stay overnight.
- Individual variation: This calculator provides estimates. Actual BAC varies significantly.
- Medication interactions: Many medications intensify alcohol effects. Check with your pharmacist.
Frequently Asked Questions
How does a BAC calculator work?
The calculator uses the Widmark formula: BAC = (grams of alcohol / (body weight in grams × distribution ratio)) × 100, minus (hours elapsed × 0.015). The distribution ratio (r) is 0.68 for males and 0.55 for females, reflecting differences in body water composition. One standard drink equals 14 grams of alcohol. The 0.015% per hour metabolism rate is an average and varies by individual.
What counts as one standard drink in the BAC calculator?
One standard drink contains 14 grams of pure alcohol. That equals roughly 12 oz of regular beer (5% ABV), 5 oz of wine (12% ABV), or 1.5 oz of distilled spirits (40% ABV). When you select a drink type in the calculator, it automatically uses the corresponding alcohol content to compute how many standard drinks you have consumed.
How long does it take for BAC to reach zero?
The calculator estimates time to sober based on your current BAC divided by the average elimination rate of 0.015% per hour. For example, a BAC of 0.08% would take roughly 5–6 hours to reach zero. However, this is an estimate — individual metabolism, food intake, hydration, and liver health all affect actual clearance time. Sleep does not speed up elimination.
Is the BAC calculator accurate enough to determine if it's safe to drive?
No. This calculator provides an educational estimate only and should never be used to decide whether to drive. Individual variation in alcohol metabolism can be significant. The only reliable way to know your BAC is a certified breathalyzer or blood test. If you have consumed alcohol, the safest choice is not to drive regardless of your estimated BAC.
Why does gender affect the BAC calculation?
Women typically have a lower Widmark r-factor (0.55) compared to men (0.68) because women generally have a higher body fat percentage and less total body water. Since alcohol is water-soluble, it becomes more concentrated in women’s blood for the same amount consumed relative to body weight, resulting in a higher BAC.