Your body eliminates alcohol at a fixed rate — roughly 0.15‰ per hour (about 0.015% BAC/hr). This rate is determined by the enzyme alcohol dehydrogenase (ADH) in your liver and cannot be accelerated by coffee, cold showers, exercise, or food. According to the National Institute on Alcohol Abuse and Alcoholism (NIAAA), this elimination rate is remarkably consistent across individuals, varying only slightly based on genetics, liver health, and chronic alcohol exposure. What this means in practice: if your peak BAC reaches 0.8‰ after an evening of drinking, it will take approximately 5–6 hours to return to zero. A common misconception is that "sleeping it off" makes you sober faster — in reality, sleep doesn't change the elimination rate, though it does prevent you from consuming more. Several factors affect how long it takes to reach zero BAC. Body weight matters because heavier individuals dilute alcohol across more body water, resulting in lower peak BAC from the same amount consumed. Biological sex plays a role too — women typically have a higher percentage of body fat and less body water, leading to higher BAC from equivalent consumption (Widmark, 1932). Food in the stomach slows absorption but doesn't change elimination speed. The Widmark formula, developed by Swedish chemist Erik Widmark, remains the standard method for estimating BAC. It accounts for the total grams of alcohol consumed, body weight, a gender-specific distribution ratio (r-factor), and time elapsed. AlcoInsights uses this formula with customizable presets to give you a personalized estimate of when you'll be sober. Sources: NIAAA "Understanding Alcohol's Effects," Widmark (1932) "Principles and Applications of Medicolegal Alcohol Determination."