BAC Calculator

About the BAC Calculator

Blood Alcohol Content (BAC) measures the concentration of alcohol in your bloodstream as a percentage. At 0.08% BAC, reaction time, coordination, and judgment are significantly impaired — the legal driving limit in the USA, UK, Canada, and Australia. Our BAC calculator estimates your current blood alcohol level based on drinks consumed, time elapsed, your weight, and biological sex, helping you make safer decisions about driving or other activities.

How It Works

The Widmark formula calculates BAC: BAC = (Alcohol consumed in grams / (Weight in grams × r)) × 100, where r = 0.68 for men and 0.55 for women (body water distribution factor). Alcohol is then reduced by metabolism: approximately 0.015% per hour for most adults. A standard drink in the USA contains 14g of pure alcohol (12 oz beer at 5%, 5 oz wine at 12%, or 1.5 oz spirits at 40%).

Tips & Best Practices

• ✓Food in the stomach slows alcohol absorption significantly — eating before drinking reduces peak BAC.
• ✓BAC decreases at roughly 0.015-0.017% per hour regardless of coffee, cold showers, or exercise.
• ✓Legal driving limits: USA/Canada/Australia 0.08%; UK 0.08% (0.05% in Scotland); many EU countries 0.05%.
• ✓Visible impairment starts at 0.05-0.06% for most people; judgment impaired well below legal limits.
• ✓This calculator estimates BAC — individual variation in metabolism means actual BAC can differ significantly.

Who Uses This Calculator

Designated drivers calculating when they are legally sober, event hosts monitoring guest alcohol intake, harm reduction educators, and researchers studying alcohol metabolism all use BAC calculators as a decision-support tool. Never use a calculator as a definitive substitute for not driving after drinking.