Blood Alcohol Content (BAC) Calculator
The Blood Alcohol Content (BAC) calculator uses the Widmark formula to estimate the concentration of alcohol in your bloodstream based on your sex, body weight, number of standard drinks consumed, and the time elapsed since your first drink. A standard drink contains 14 grams of pure alcohol — equivalent to a 355 mL regular beer, a 148 mL glass of wine, or a 44 mL shot of spirits.
The body eliminates alcohol at an average rate of 0.015% BAC per hour. The Widmark factor (r) accounts for the different proportions of body water between males (r = 0.68) and females (r = 0.55), reflecting differences in body composition. This estimate is for educational purposes only; individual results vary significantly based on factors such as food intake, hydration, medication, and genetics.
How it works
BAC (%) = [drinks × 14 g] ÷ [weight_kg × 1000 × r] × 100 − 0.015 × hours. Where r = 0.68 (male) or 0.55 (female). Result is clamped to 0 if negative (alcohol fully metabolised).
Use cases
- Understanding how many drinks raise BAC above the legal driving limit
- Estimating how long to wait before driving after consuming alcohol
- Health education and awareness about alcohol metabolism
- Comparing the effect of body weight and sex on alcohol absorption
- Academic or research reference for the Widmark BAC formula