What is the legal BAC limit for driving in different countries?
UK: 0.08% (80 mg/100 ml blood) in England, Wales, and Northern Ireland; 0.05% in Scotland. US: 0.08% federally (Utah: 0.05%). EU: most countries 0.05%; Czech Republic, Hungary, Slovakia: 0.00%. Australia: 0.05% (0.00% for learners and professional drivers). Japan: 0.03%. China: 0.02% drink-driving, 0.08% drunk-driving. Many countries are moving toward lower limits.
How long does alcohol stay in your system?
Your liver metabolises alcohol at a fixed rate of approximately 0.015–0.017% BAC per hour (roughly one standard drink per hour). At 0.08% BAC, it takes over 5 hours to reach 0.00% — you cannot speed this up with coffee, food, or exercise. For breathalyser tests: alcohol is detectable for 12–24 hours. For blood tests: 12–48 hours. Urine tests: 12–48 hours (ethyl glucuronide tests can detect for 80 hours).
Does food affect BAC?
Yes — significantly. Eating a meal before or during drinking slows alcohol absorption by 50–75%. Food delays gastric emptying, giving the body more time to metabolise alcohol before it reaches the bloodstream. Fatty foods are most effective. However, food does not affect the rate of elimination — once absorbed, alcohol is metabolised at the same fixed rate regardless of what you eat.
Why do women generally have higher BAC than men after the same drinks?
Several biological factors cause women to absorb more alcohol and reach higher BAC: lower body water percentage (52% vs 61% in men — alcohol distributes in water), lower levels of the stomach enzyme alcohol dehydrogenase that breaks down alcohol before absorption, and typically lower body weight. These differences mean the same number of drinks produces meaningfully higher BAC in women, which the Widmark formula accounts for.
How accurate is a BAC calculator?
BAC calculators provide estimates, not exact measurements. Actual BAC varies with metabolism rate (±25–30% between individuals), drink strength variations, drinking speed, and hydration status. The only legally accepted measurement is a certified breathalyser or blood test. Never use a calculator to decide whether to drive — if you have been drinking, the safest choice is not to drive.