BAC Calculator – Estimate Blood Alcohol Concentration
Free BAC calculator: enter your gender, weight, number of drinks and hours elapsed to estimate your blood alcohol concentration. Uses the Widmark formula. For education only. Never drive after drinking. No sign-up, runs in your browser.
BAC Calculator
Estimate blood alcohol content from gender, weight, drinks and time. For educational use only.
How the BAC calculator works
Widmark formula: BAC = (A × 5.14 / (W × r)) − 0.015 × H. A = alcohol in grams, W = body weight in kg, r = distribution factor (0.68 male, 0.55 female), H = hours elapsed. The 0.015 factor approximates alcohol elimination (about 0.015% per hour).
Understanding BAC and alcohol metabolism
Blood alcohol concentration (BAC) is the percentage of alcohol in your bloodstream. In the US, 0.08% is the legal limit for driving in most states, but impairment begins at lower levels. At 0.02%, some people experience relaxed mood and slight loss of judgment. At 0.05%, coordination and reaction time are affected. At 0.08%, balance, vision and judgment are clearly impaired.
Alcohol is metabolized at roughly 0.015% per hour on average, though this varies by person. Food in the stomach slows absorption. The Widmark formula used here is a simplified model; actual BAC depends on many factors including genetics, medications, and hydration. Breathalyzers and blood tests are the only accurate measures.
This calculator is for educational purposes only. Never use it to decide whether to drive. If you drink, plan ahead: designate a driver, use public transport, or stay overnight. The only safe BAC for driving is zero.