Use this free online BAC calculator to estimate your blood alcohol content using the Widmark formula, based on your gender, body weight, number of standard drinks, and the hours elapsed since you started drinking. This tool is intended for general educational purposes only and must never be used to determine whether you are fit to drive.
This is an educational estimate only, not a precise measurement — actual BAC varies by individual metabolism, food intake, and other factors. Never drive after drinking, regardless of this estimate.
1 standard drink ≈ 14g of alcohol
How to Use the BAC Calculator
Select your Gender from the dropdown.
Enter your Body Weight in kilograms in the "Body Weight (kg)" field.
Enter the Number of Standard Drinks you've had (1 standard drink ≈ 14g of alcohol).
Enter the Hours Elapsed Since Drinking Started.
Click "Calculate BAC" to view your estimated blood alcohol content.
Frequently Asked Questions
This calculator uses the Widmark formula, which estimates blood alcohol content from the grams of alcohol consumed, your body weight, a gender-based distribution ratio (0.68 for men, 0.55 for women), and subtracts the amount your body metabolizes over time (about 0.015% per hour).
No. This BAC calculator gives an educational estimate only and does not account for individual differences in metabolism, food intake, medications, or overall health. It should never be used to determine whether you are fit to drive — never drive after drinking, regardless of this estimate.
If you leave the body weight, drinks, or hours fields blank, or enter a zero or negative body weight, or negative drinks or hours, the calculator displays an error message asking you to enter valid values instead of a result.
Yes, this tool is completely free, requires no sign-up, and can be used as many times as you like.