Blood Alcohol Content (BAC) Calculator
This calculator provides an estimate for educational purposes ONLY. Do not rely on this tool to determine if you are safe to drive.
Your BAC Estimation
Enter your details above for an estimation of your Blood Alcohol Content.
What is Blood Alcohol Content (BAC)?
Blood Alcohol Content, or BAC, is the percentage of alcohol in a person's bloodstream. A BAC of 0.10% means that there is 1 part alcohol for every 1000 parts blood. Your BAC is influenced by many factors, including your weight, sex, the number of drinks you've had, and the time over which you consumed them.
How This BAC Calculator Works
This calculator uses the **Widmark formula**, a well-established method for estimating BAC. The formula is:
BAC = (Alcohol consumed in grams / (Body weight in grams × R)) × 100
Where **R** is the gender-specific water distribution ratio (0.55 for females, 0.68 for males). Our calculator then subtracts the amount of alcohol eliminated by the liver over the time period you specify (approx. 0.015% per hour).
What is a "Standard Drink"?
This is where many people miscalculate their intake. A "standard drink" in the U.S. contains 14 grams of pure alcohol. This is equivalent to:
| Beverage Type | Serving Size | Approx. Alcohol By Volume (ABV) |
|---|---|---|
| Regular Beer | 12 oz / 355 mL | 5% |
| Wine | 5 oz / 148 mL | 12% |
| Distilled Spirits (Liquor) | 1.5 oz / 44 mL | 40% |
Note that craft beers, certain wines, and mixed drinks can have much higher alcohol content and should be accounted for accordingly (e.g., one strong IPA could be equivalent to 1.5 or 2 standard drinks).
Understanding Impairment Levels
Even small amounts of alcohol affect your judgment and coordination. Knowing these general impairment levels reinforces why it is never safe to drink and drive.
- 0.02% - 0.03%: Mild relaxation and mood elevation. Some loss of judgment.
- 0.05% - 0.06%: Lowered alertness, exaggerated behavior, loss of small-muscle control.
- 0.08% - 0.10%: Poor muscle coordination, impaired judgment and reasoning, loss of balance. Illegal to drive in all 50 US states.
- 0.15% - 0.20%: Significant impairment of motor control and major loss of balance.
Factors like your metabolism, medications, and recent food intake can all affect your BAC. Overall health, as indicated by metrics like your BMI, can also play a role.
Legal and Safety Disclaimer
This tool provides an estimate for informational and educational purposes only. It is not a legal definition or a guarantee of your actual BAC. The calculation is based on averages and cannot account for all individual biological factors. The result should **NEVER** be used to determine whether it is safe for you or anyone else to operate a motor vehicle or heavy machinery. If you have been drinking, do not drive. Use a designated driver, a taxi, or a rideshare service.