Estimate Your BAC
Frequently Asked Questions
What does Blood Alcohol Content (BAC) actually measure?
BAC is the percentage of alcohol in your bloodstream by volume. For example, 0.08% means 0.08 grams of alcohol per 100mL of blood. This measurement determines legal impairment thresholds. In most jurisdictions, 0.08% is the legal driving limit; 0.05% shows measurable impairment even if not legally drunk. BAC reflects total alcohol consumed minus what your liver eliminates (about 1 drink per hour).
Why do men and women metabolize alcohol differently?
Women typically reach higher BAC than men consuming identical amounts due to: (1) lower body water percentage (alcohol distributes in water, not fat), (2) lower gastric alcohol dehydrogenase enzyme (metabolizes alcohol before absorption), (3) hormonal effects on metabolism varying with menstrual cycle. Women can have 20-30% higher BAC at the same consumption level. Medications, liver disease, and food also significantly affect metabolism.
How accurate is this calculator compared to a breathalyzer?
This uses the Widmark formula, the gold standard for BAC estimation. However, actual BAC varies ±10-15% due to individual metabolism differences. Breathalyzers measure actual breath alcohol and are significantly more accurate. This calculator is best for understanding relative impairment and recovery time. For legal/safety decisions, use an actual breathalyzer or observe sobriety tests (coordination, eye tracking).
Can eating food after drinking reduce BAC?
No. Food consumed AFTER drinking doesn't reduce BAC because alcohol is already absorbed. Food eaten BEFORE or DURING drinking slows absorption, extending the time to peak BAC and reducing maximum BAC by 20-40%. The liver still eliminates one drink per hour regardless of food. Once alcohol is in your bloodstream, only time eliminates it—not food, coffee, cold showers, or exercise.
Why is liver function critical for alcohol metabolism?
Your liver metabolizes ~90% of consumed alcohol; kidneys/lungs eliminate ~10%. The liver processes alcohol at a fixed rate (about 1 standard drink/hour) that can't be accelerated by hydration, exercise, or willpower. Pre-existing liver disease (hepatitis, cirrhosis, fatty liver) severely reduces alcohol elimination, causing dangerously high BAC accumulation. Certain medications also interfere with liver metabolism. If you have liver concerns, discuss alcohol with a physician.
At what BAC level is driving legally impaired?
In most countries, 0.08% is the legal driving limit for adults (21+ in US). However, impairment begins much earlier: coordination effects at 0.02-0.03%, reduced judgment at 0.04-0.06%, significant impairment at 0.07-0.09%. Many insurance and legal experts recommend 0.05% as a personal safety threshold. Driving under 0.05% with any alcohol consumption is safest. Never rely on feeling "fine"—impairment is often invisible to yourself.