Blood Alcohol Content Calculator

The Blood Alcohol Content (BAC) Calculator estimates your blood alcohol concentration based on the number of standard drinks, body weight, biological sex, and time elapsed. This tool helps adults understand their impairment level and legal driving status. Use it to track sobriety after a party, plan safe transportation, or check if you are sober enough to drive the next morning.

Number of Standard Drinks One standard drink equals 14g of pure alcohol (12oz beer, 5oz wine, or 1.5oz liquor)

Body Weight Enter your body weight

Weight Unit

Biological Sex Different body compositions affect alcohol metabolism

Hours Since First Drink How many hours have passed since you started drinking

Hours Since Last Drink How many hours have passed since your last drink

Quick Examples:

How Blood Alcohol Content Is Calculated

Blood Alcohol Content (BAC) represents the percentage of alcohol present in your bloodstream. This calculator utilizes the Widmark Formula, a widely accepted method in forensic science, to estimate your level accurately.

BAC = [(Drinks × 5.14) / (Weight × r)] - .015 × Hours

Where:

5.14: Conversion factor for alcohol density in the blood.
r: Gender constant (0.73 for men, 0.66 for women).
0.015: Average alcohol elimination rate per hour.

The calculation first determines the total grams of alcohol consumed. It then adjusts this number based on your body weight and gender because alcohol distributes differently in body water. Finally, the calculator subtracts the amount of alcohol your liver has metabolized over the elapsed time. This provides a scientifically grounded estimate of your current impairment.

What Your Blood Alcohol Content Means

Your BAC number indicates the concentration of alcohol in your system and predicts your level of physical and mental impairment.

Assessing Impairment

A result below 0.02% typically indicates minimal effects, whereas a range of 0.05% to 0.08% shows clear loss of coordination and judgment. If your result hits 0.08% or higher, you are legally intoxicated in most US states and must not drive.

Planning for Safety

Use the "hours until sober" metric to set a hard deadline for leaving an event. For example, if your BAC is 0.10%, you generally need at least 6 to 7 hours after stopping drinking to return to 0.00%.

Morning Check

If you drank heavily the night before, use the tool to check your current status. You may still be over the legal limit the next morning, even if you feel awake.

This calculator is for informational purposes only and is not a substitute for a professional breathalyzer test. Actual BAC can vary based on health, food intake, and individual metabolism. Never rely solely on this estimate to determine if it is legal or safe to drive.

Always err on the side of caution and wait until your BAC is 0.00% before driving or operating heavy machinery.