BAC Calculator
Estimate your blood alcohol content from what you have had to drink, your weight and how long you have been drinking, and see roughly how long it takes to return to zero.
Drinks
How to estimate your BAC
- Choose your body type and enter your weight.
- Add each drink: how many, the type, and if needed the size and alcohol percentage. Enter how many hours you drank over and how long it has been since the first drink.
- Read the estimated BAC now, the peak, and roughly how long until you are back to zero. The chart shows the whole curve.
How BAC is estimated
This calculator uses the Widmark formula, the standard method in road safety and forensic estimates. It divides the grams of alcohol you drank by your body weight times a distribution factor (about 0.68 for men and 0.55 for women, because of differences in body water), then subtracts about 0.015% for every hour, the average rate the liver removes alcohol. Drinks are assumed to be spread evenly over the time you were drinking.
One US standard drink contains 14 grams of pure alcohol: a 12 oz beer at 5%, a 5 oz glass of wine at 12%, or a 1.5 oz shot of 40% spirits. Craft beers, large pours and strong cocktails can easily be two or more standard drinks each.
Why your real BAC may differ
- Food slows absorption and lowers the peak; drinking on an empty stomach raises it.
- Elimination rates vary from about 0.010% to 0.025% per hour between people.
- Body composition, medications, illness, fatigue and genetics all play a part.
- Alcohol keeps being absorbed for 30–90 minutes after your last drink, so BAC can still be rising when you stop.
Only time lowers BAC. Coffee, cold showers, food after drinking and sleep do not speed it up. Impairment starts well below legal limits; at 0.02% judgment and reaction time are already affected.
Legal driving limits
| Place | Limit for most drivers |
|---|---|
| United States (except Utah) | 0.08% |
| Utah | 0.05% |
| Canada (criminal limit) | 0.08%; most provinces penalize from 0.05% |
| United Kingdom (England, Wales, N. Ireland) | 0.08% |
| Scotland, most of Europe, Australia | 0.05% |
Many places set lower or zero limits for young, new and commercial drivers. The safest limit for driving is zero.
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Frequently asked questions
Can I use this to decide if I can drive?
No. It is an educational estimate and can be wrong by a wide margin for any individual. If you have been drinking, don’t drive: use a taxi, rideshare, public transport or a sober driver.
How long does it take to sober up?
On average about one hour per standard drink after you stop, but it varies. The “back to 0.00%” time shows the estimate for your drinks.
Why do women reach a higher BAC from the same drinks?
On average women have less body water per pound, so the same alcohol is more concentrated in the blood.
Does eating lower my BAC?
Eating before or while drinking slows absorption and lowers the peak. Eating afterwards does not speed up how fast alcohol leaves your body.
Is anything sent to a server?
No. Everything is calculated in your browser, and nothing you enter leaves your device.