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Blood Alcohol (BAC) Calculator
Estimate your BAC. This is for informational purposes only and is not a legal definition or recommendation.
What is it?
Blood Alcohol Concentration (BAC) represents the amount of alcohol present in your bloodstream, expressed as a percentage. For example, a BAC of 0.08% means that 0.08% of your blood is pure alcohol. This number helps determine how impaired you may be after drinking.
The BAC Calculator — also known as a blood alcohol calculator, blood alcohol level calculator, or BAC level calculator — estimates your BAC based on factors such as the number of drinks you’ve had, your body weight, sex, and how long you’ve been drinking. It’s a quick, educational tool to help you understand your level of intoxication before deciding to drive or engage in other activities that require alertness.
Why it matters
Knowing your estimated BAC isn’t just about numbers — it’s about safety, responsibility, and awareness. Even a small increase in BAC can slow your reflexes and impair judgment. Understanding your BAC can help prevent risky decisions like driving under the influence, protect your health, and keep others safe.
This tool is particularly useful for social drinkers, party-goers, and anyone wanting to drink responsibly. It helps you gauge when it’s safe to drive or when you might need more time for your body to metabolize the alcohol.
The BAC Calculator estimates your blood alcohol concentration using the Widmark Formula:
| Variable | Meaning |
|---|---|
| A | Total alcohol consumed (in grams) |
| r | Body water constant (0.68 for men, 0.55 for women) |
| W | Body weight (in kilograms) |
| H | Hours since first drink |
The formula looks like this: BAC = (A / (r × W)) × 100 - (0.015 × H)
For instance, if you’ve had 3 beers over two hours and weigh 70 kg, your estimated BAC may be around 0.05% — enough to affect reaction time and concentration, even if you still “feel fine.” This is why calculators like this exist: to help you visualize what “just a few drinks” can mean physiologically.