Alcohol Metabolism Calculator

How Alcohol Metabolism Rate Is Calculated

The liver metabolizes alcohol at a relatively fixed rate regardless of body size, tolerance, or coffee consumption. Understanding this rate helps estimate when blood alcohol returns to zero.

Alcohol Elimination Rate: The average person eliminates approximately 0.015–0.020 BAC (Blood Alcohol Concentration) per hour.

BAC Calculation (Widmark Formula): BAC = (Alcohol consumed in grams) / (Body weight kg × r × 10)

Where r = gender factor:

• Males: r = 0.68
• Females: r = 0.55

Standard Drink = ~14g of pure alcohol (US standard):

• 355 mL (12 oz) beer at 5% = ~14g
• 148 mL (5 oz) wine at 12% = ~14g
• 44 mL (1.5 oz) spirits at 40% = ~14g

Worked Example: 80 kg male drinks 4 standard drinks over 2 hours:

• Alcohol consumed = 4 × 14g = 56g
• BAC = 56 / (80 × 0.68 × 10) = 56 / 544 = 0.103%
• Elimination over 2 hours: 0.015 × 2 = 0.030
• BAC at end of drinking: 0.103 - 0.030 = 0.073%
• Time to reach 0.00%: 0.073 / 0.015 = 4.9 more hours

That 0.073% is the number worth sitting with. It is under the American limit and over the Australian one, on the same body, at the same moment. Pick the limit for where you actually are in the input above.

Legal BAC limits vary more than people expect:

• USA, Canada, England and Wales, Mexico: 0.08%
• Most of Europe, Australia, Scotland, Israel: 0.05%
• Japan, India, Serbia: 0.03%
• Sweden, Norway, Poland, China: 0.02%
• Czechia, Hungary, Romania, and new or professional drivers in most countries: effectively zero

Nothing speeds up elimination. Not coffee, not a cold shower, not exercise, not a big meal afterwards. The liver’s alcohol dehydrogenase works at a rate that is close to saturated after the first drink, which is why the decay is a straight line rather than a curve. Coffee makes an impaired person an alert impaired person, and that is arguably worse, because it removes the tiredness that would otherwise keep them off the road.

Food is the one thing that matters, and only beforehand. Eating before you drink slows gastric emptying, so the alcohol reaches the small intestine gradually rather than all at once. Peak BAC can come out a third to a half lower on a full stomach than an empty one, for exactly the same drinks. This calculator assumes the worst case and does not model it, so treat every number here as the optimistic end of the range.

Why the morning-after arrest happens. Finish drinking at 2 AM at 0.14% and you are still at about 0.05% at 8 AM. Six hours of sleep clears roughly 0.09%, not the lot, and you will feel fine long before you are legal.