Blood Alcohol (BAC) Calculator
Estimate blood alcohol concentration with the Widmark formula from your weight, sex, drinks, and time. For education only, not a measure of fitness to drive.
Calculator by Toolsloft ↗- Estimated BAC
- 0.047 (Under 0.08)
This is an educational estimate. It does not measure whether you are safe or legal to drive. If you have been drinking, do not drive.
Blood alcohol concentration depends on how much you drank, your body size, your sex, and how long your body has had to process it. This tool applies the Widmark formula to estimate BAC. It is an educational estimate and should never be used to decide whether to drive.
How this is calculated
The Widmark formula divides the grams of alcohol consumed by body weight in grams times a distribution ratio, then multiplies by 100 for a percentage. The ratio is 0.68 for men and 0.55 for women. A US standard drink is 14 grams of ethanol. The body clears roughly 0.015 percent per hour, which is subtracted for the time since your first drink. Real BAC varies with food, metabolism, and medication.
How to use
- Enter your body weight in kilograms and select your sex.
- Enter the number of US standard drinks and hours since your first drink.
- Read the estimated BAC and whether it is over the 0.08 driving limit.
Examples
- 80 kg man, 3 drinks, 2 hours:
Estimated BAC 0.047 (Under 0.08) - 90 kg man, 5 drinks, 1 hour:
Estimated BAC 0.099 (Over 0.08)
FAQ
- Can I use this to decide if I am safe to drive?
- No. This is an estimate for education only. Individual results vary widely, and impairment starts well below any legal limit. If you have been drinking, do not drive.
- What is a standard drink?
- In the US a standard drink is about 14 grams of pure alcohol, which is roughly a 12 oz beer, a 5 oz glass of wine, or a 1.5 oz shot of spirits.