How is BAC calculated?

It uses the Widmark formula: grams of pure alcohol divided by (body weight in grams times a body-water constant), times 100, minus roughly 0.015 percent per hour for metabolism. The constant is about 0.68 for men and 0.55 for women.

Can I use this to decide whether to drive?

No. The result is a rough estimate that ignores food, hydration, medication, genetics and many other factors. If you have been drinking, do not drive — the only safe BAC for driving is zero.

Is anything uploaded?

No. All calculations happen locally in your browser and nothing is sent anywhere.

Blood Alcohol Content (BAC) Calculator

Estimate blood alcohol content with the Widmark formula

This calculator estimates your blood alcohol content (BAC) from the number and strength of your drinks, your body weight and sex, and the time elapsed since your first drink. It uses the well-known Widmark formula and subtracts an average elimination rate of about 0.015% per hour.

It also shows how many grams of pure alcohol you have consumed and a rough estimate of how many hours it would take to return to sober. Everything runs in your browser — nothing is uploaded.

Important: this is an educational estimate only. Real BAC varies widely between people and situations. Never use it to decide whether you are fit to drive — if you have been drinking, do not drive.