Blood Alcohol Content Calculator
Get a rough estimate of blood alcohol concentration from what you drank. Never use it to decide whether you can drive.
How to use the Blood Alcohol Content Calculator
- Choose the sex.
- Enter the body weight and pick its unit.
- Choose the enter drinks as.
- Enter the standard drinks – 12 oz beer (5%), 5 oz wine (12%) or 1.5 oz spirits (40%) = 1 drink.
- Enter the total volume consumed and pick its unit.
- Enter the alcohol by volume.
- Enter the hours since first drink.
- Press Calculate. The result updates automatically as you type.
About the Blood Alcohol Content Calculator
Blood alcohol concentration depends on how much alcohol you drink, how much water your body contains to dilute it, and how long your liver has had to break it down. The Widmark formula combines those three factors. Real BAC can differ substantially because of food in the stomach, drinking speed, medications, liver health, body composition and individual metabolism.
Important: impairment starts well below the legal limit, and many states and countries use limits lower than 0.08% (Utah uses 0.05%; commercial drivers 0.04%; drivers under 21 have zero tolerance). The only safe choice is not to drive after drinking. If someone is confused, vomiting, has slow or irregular breathing or cannot be woken, call 911 immediately.
Formula
BAC (%) = [alcohol (g) ÷ (body weight (g) × r)] × 100 − 0.015 × hours
This is the Widmark formula. r is the body water distribution ratio (about 0.68 for men and 0.55 for women), and 0.015% per hour is an average elimination rate. One U.S. standard drink contains 14 g (0.6 fl oz) of pure alcohol; alcohol grams from volume = mL × ABV × 0.789 g/mL.
Example calculation
Using the default values:
- Sex = Male
- Body weight = 160 lb
- Enter drinks as = Number of standard drinks
- Standard drinks = 3
- Hours since first drink = 2 hours
the calculator returns:
- Estimated BAC: 0.055%
- Typical effects: Lowered inhibitions, reduced coordination and judgment
- Approximate time until 0.00%: 3 h 40 min from now
- Alcohol consumed: 42 g
- Standard drinks: 3
Frequently asked questions
How long does it take to get alcohol out of your system?
On average the body lowers BAC by about 0.015% per hour, roughly one standard drink per hour. Coffee, water, food and cold showers do not speed this up.
Why do women reach a higher BAC from the same drinks?
On average women have a lower proportion of body water, so the same amount of alcohol is more concentrated in their blood.
Can I use this to see if I can drive?
No. It gives only a rough population-average estimate, and impairment begins before the legal limit. If you have been drinking, use a designated driver, rideshare or public transit.
Last updated: · Category: Health & Fitness calculators