BAC Calculator
This BAC calculator estimates blood alcohol concentration from your sex, body weight, number of standard drinks and hours since your first drink using the Widmark formula; it is an approximation only and must never be used to decide whether you can drive.
About this tool
This BAC calculator estimates blood alcohol concentration from your sex, body weight, number of standard drinks and hours since your first drink using the Widmark formula; it is an approximation only and must never be used to decide whether you can drive.
How to use it
- Choose your sex and enter your body weight.
- Enter the number of standard drinks you have had.
- Enter the hours since your first drink.
- Read the estimated BAC, the impairment level and the time until it reaches zero.
Good to know
- One standard drink here is 14 g of alcohol — about 355 ml of beer, 150 ml of wine or 45 ml of spirits.
- Widmark estimate: BAC % = alcohol (g) ÷ (body weight in g × r) × 100, with r = 0.68 for men and 0.55 for women.
- The body eliminates about 0.015% BAC per hour, and the calculator subtracts this for the hours entered.
- Real BAC depends on food, drinking speed, medications and individual metabolism, so actual levels can be higher than estimated.
Runs entirely in your browser — nothing you enter is uploaded or stored.
Frequently asked questions
How long does it take for alcohol to leave your system?
The body clears roughly 0.015% BAC per hour — about one standard drink per hour for many adults. Coffee, water, cold showers or sleep do not speed this up.
Can I use a BAC calculator to know if I can drive?
No. Calculators only estimate and can underestimate your real level; impairment also starts well below legal limits. If you have been drinking, do not drive.
Why do women reach a higher BAC than men?
On average, women have less body water per kilogram, so the same amount of alcohol produces a higher concentration. The Widmark formula reflects this with a lower distribution factor.
What is the legal BAC limit?
Many countries set the driving limit at 0.05%, the United States generally at 0.08%, and some countries at or near zero. Stricter limits often apply to new and professional drivers.