80 kg man, four 330 ml beers (5%), 2 hours since the first
About 0.066% now, 0.096% at peak, and around 4 hours 23 minutes more to zero.
Blood alcohol (BAC) calculator
—
Blood alcohol is estimated with the Widmark formula: grams of alcohol ÷ (body weight in grams × 0.68 for men or 0.55 for women) × 100, minus 0.015% for each hour since the first drink. Food, medicines, health and genetics change the real figure a lot. Never use this to decide whether you are fit to drive.
Sex
kg
Estimated blood alcohol
0.066%
About 4 h 23 min more until the estimate reaches zero. That is over the 0.05% limit in most of Europe and Australia. Never drive after drinking.
- Pure alcohol
- 52 g
- Standard drinks (14 g)
- 3.7
- Peak estimate
- 0.096%
- Hours to zero
- 4 h 23 min
0 h3 h7 h
This is a rough estimate for education only. It cannot tell you that you are safe to drive, work or look after others.
What a BAC estimate can and cannot tell you
Blood alcohol content, or BAC, is the share of your blood that is alcohol. A BAC of 0.08% means 0.08 g of alcohol in every 100 ml of blood. The Widmark formula estimates it from how much you drank, your weight and sex, and how much time has passed.
An 80 kg man who has four 330 ml bottles of 5% beer has drunk about 52 g of alcohol, about 3.7 US standard drinks. That peaks near 0.096%. Two hours after the first drink it is about 0.066%, and it would take about another 4 hours 23 minutes to fall to zero at the average rate.
The same drinks hit a lighter person, or a woman of the same weight, harder, because there is less body water to spread the alcohol through. Drinking on an empty stomach makes the peak higher and earlier.
Use this to understand how alcohol builds up and how slowly it leaves, not to test yourself. The only safe amount before driving is none. If you will drink, plan a taxi, public transport or a sober driver in advance.
Sources
What this calculator does not account for
- Food, medicines, health and genetics.
- Drinks poured larger or stronger than listed.
- Whether you are fit to drive, which it can never tell you.
How this is calculated
Formula: The Widmark formula
BAC % =A ÷ (W × r) × 100 − 0.015 × tWhat the symbols mean
- AGrams of alcohol: ml × strength % ÷ 100 × 0.789.
- WBody weight in grams.
- rBody water ratio: 0.68 for men, 0.55 for women.
- tHours since the first drink.
Good to know
- 0.015% an hour is an average rate of clearing alcohol.
- For weekly units, use the alcohol units calculator.
Read the full methodologyFound an error? Contact us
Worked examples
Each example is worked out by the same code as the calculator above.
Embed this calculator
The frame shows the tool only.
<iframe src="/embed/bac-calculator" title="BAC calculator" width="100%" height="720" style="border:0;max-width:42rem" loading="lazy"></iframe>Questions
How is blood alcohol calculated?
With the Widmark formula: grams of alcohol divided by body weight times a body-water factor, minus about 0.015% for each hour since drinking began.
How long does it take for alcohol to leave your body?
On average the body clears about 0.015% BAC an hour, roughly one standard drink an hour. Coffee, water or a cold shower do not speed it up.
How many beers to reach 0.08?
It depends on weight, sex and time. For an 80 kg man, four 330 ml beers at 5% peak near 0.096% if drunk quickly.
What is the legal limit for driving?
0.08% in the US and England, 0.05% in most of Europe and Australia, and 0.03% in India. Any amount affects driving.
Can I use this to know if I can drive?
No. Real levels vary widely with food, medicine and health. If you have been drinking, do not drive.