Why use this calculator
Estimating your BAC helps you make informed decisions about driving and understand how alcohol affects your body based on weight, sex, and consumption rate.
How to use it
Select your preferred unit system (metric or imperial), then enter your weight, sex, number of standard drinks consumed, the type of drink, and hours since your first drink. The calculator uses the Widmark formula to estimate your current BAC.
The formula
Widmark Formula: BAC = (Drinks x Oz of Alcohol x 5.14) / (Body Weight x r) - 0.015 x Hours. r = 0.73 for males, 0.66 for females. One standard drink = 0.6 oz of pure alcohol.
Worked examples
170 lb male, 3 beers over 2 hours
Estimated BAC of about 0.04, under the legal limit
130 lb female, 2 glasses of wine over 1 hour
Estimated BAC of about 0.06, approaching the legal limit
When people use it
- Deciding whether it is safe to drive after drinking
- Understanding how body weight affects alcohol tolerance
- Planning responsible alcohol consumption at events
- Educational purposes about alcohol metabolism
Tips
- This is an estimate only; actual BAC depends on many individual factors including food intake and metabolism
- The only way to be truly safe is not to drive after any alcohol consumption
- Food in your stomach slows alcohol absorption but does not reduce total BAC
- Hydrating between drinks can reduce side effects but does not lower BAC faster
Questions people ask
- How accurate is this BAC calculator?
- It provides a rough estimate. Actual BAC varies based on food intake, medications, liver health, and individual metabolism. Never rely solely on a calculator to determine if you are safe to drive.
- How long does it take to metabolize one drink?
- On average, the body metabolizes alcohol at about 0.015 BAC per hour, which is roughly one standard drink per hour.
- What is a standard drink?
- A standard drink contains about 0.6 oz of pure alcohol: 12 oz of beer (5%), 5 oz of wine (12%), or 1.5 oz of spirits (40%).