BAC Calculator
Blood alcohol content · Time to sober · Legal limit check
🍺 Enter your weight, sex, drinks, and time since your first drink to estimate your BAC and time until sober.
What This BAC Calculator Estimates
Blood alcohol content (BAC), also called blood alcohol concentration, is the amount of alcohol in your blood, measured in grams per deciliter. A BAC of 0.08 means 0.08 grams of alcohol per 100 milliliters of blood. Police measure it with a breath test or a blood test.
This calculator estimates BAC from what you drank, your weight and sex, and how long ago you started. It shows your BAC now, the value before your liver removed any alcohol, how long until you drop below a legal limit and reach zero, and the clock time for each. A chart plots your BAC hour by hour.
The result is an estimate from population averages. Two people of the same weight can have different BACs after the same drinks, so never use this number to decide whether to drive.
Widmark BAC Formula
Grams of alcohol in a drink
Worked example
A 140 lb woman who has the same 4 drinks reaches about 0.160 percent before elimination and 0.130 percent after 2 hours, nearly 60 percent higher.
BAC Chart: Drinks to Reach 0.08
Standard drinks consumed within 1 hour to reach 0.08 percent, by weight, using the Widmark formula.
| Weight | Men | Women |
|---|---|---|
| 120 lb (54 kg) | 2.5 | 2.0 |
| 140 lb (64 kg) | 2.9 | 2.4 |
| 160 lb (73 kg) | 3.3 | 2.7 |
| 180 lb (82 kg) | 3.8 | 3.0 |
| 200 lb (91 kg) | 4.2 | 3.4 |
| 220 lb (100 kg) | 4.6 | 3.7 |
| 240 lb (109 kg) | 5.0 | 4.1 |
One standard drink raises BAC by about 0.028 percent for a 160 lb man and 0.035 percent for a 160 lb woman before elimination.
What Counts as a Standard Drink
NIAAA defines a U.S. standard drink as any beverage with about 14 grams, or 0.6 fluid ounces, of pure alcohol. The presets in the calculator each contain one standard drink. Use the custom row for craft beer, cocktails, or large pours.
| Drink | Typical ABV | One standard drink |
|---|---|---|
| Regular beer | 5% | 12 fl oz |
| Malt liquor or hard seltzer | 7% | 8 to 10 fl oz |
| Table wine | 12% | 5 fl oz |
| Fortified wine | 17% | 3 to 4 fl oz |
| Liqueur | 24% | 2 to 3 fl oz |
| Distilled spirits | 40% | 1.5 fl oz |
Pours are often bigger than a standard drink. A 16 oz craft beer at 7 percent holds about 1.9 standard drinks, and a 9 oz glass of wine at 13 percent holds about 2.
How Long Does It Take to Sober Up?
Alcohol leaves the blood mainly through the liver at a fairly steady rate. In a review of controlled studies, Jones found 0.015 percent per hour to be a good average for moderate drinkers, with a range from 0.010 to 0.035. On an empty stomach rates tend to be 0.010 to 0.015, and people in alcohol detoxification can reach 0.025 to 0.035.
| Starting BAC | Hours to zero at 0.015/h |
|---|---|
| 0.04 | 2.7 |
| 0.08 | 5.3 |
| 0.10 | 6.7 |
| 0.15 | 10.0 |
| 0.20 | 13.3 |
NIAAA warns that cold showers, hot coffee, and walking do not reverse alcohol's effects. Only time lowers BAC, which is why you can still be over the limit the morning after heavy drinking.
Legal Limits and Crash Risk
- 0.08: illegal to drive in all U.S. states, DC, and Puerto Rico (NHTSA).
- 0.05: the limit in Utah.
- 0.04: federal limit for commercial drivers on duty (49 CFR 382.201).
NHTSA reports that drivers at 0.08 are about 4 times more likely to crash than sober drivers, and at 0.15 at least 12 times more likely. Laws outside the United States differ, so check local rules.
NIAAA defines binge drinking as a pattern that brings BAC to 0.08 or higher, typically 5 or more drinks for men or 4 or more for women in about 2 hours.
Accuracy and Limitations
- Absorption. The formula assumes all alcohol is in the blood at once. BAC usually keeps rising after the last drink, and NIAAA notes it can rise even when a person stops drinking or passes out.
- Food. Eating slows absorption and lowers the peak.
- Body composition. The r factor is an average; Maskell and colleagues found it varies between individuals of the same sex.
- Medications. Sedatives, opioids, and antihistamines increase impairment at any BAC.
Common Mistakes
- Counting glasses, not standard drinks. One large cocktail can hold 2 or 3 standard drinks.
- Timing from the last drink. Enter hours since your first drink.
- Assuming sleep resets you. 0.15 at midnight can still be about 0.06 at 6 AM.
- Feeling fine. NHTSA notes that failing to recognize impairment is itself a symptom.
If someone shows confusion, vomiting, seizures, slow or irregular breathing, or cannot stay awake, call 911. These are signs of alcohol overdose.
Frequently Asked Questions
Sources & References
- National Highway Traffic Safety Administration, Drunk Driving (effects by BAC, legal limits, crash risk, 2024 data). nhtsa.gov
- National Institute on Alcohol Abuse and Alcoholism, What Is a Standard Drink? niaaa.nih.gov
- National Institute on Alcohol Abuse and Alcoholism, Understanding the Dangers of Alcohol Overdose. niaaa.nih.gov
- Jones AW. Evidence based survey of the elimination rates of ethanol from blood. Forensic Sci Int 2010;200:1 to 20. doi.org/10.1016/j.forsciint.2010.02.021
- Maskell PD, Jones AW, Savage A, Scott Ham M. Evidence based survey of the distribution volume of ethanol. Forensic Sci Int 2019;294:124 to 131. doi.org/10.1016/j.forsciint.2018.10.033
- Code of Federal Regulations, 49 CFR 382.201 Alcohol concentration. ecfr.gov
Results are estimates for informational purposes only and are not a measure of fitness to drive or a substitute for medical advice. Reference data reviewed: 2026.