Blood Alcohol Concentration (Widmark formula)
Theoretical blood alcohol concentration from consumed volume, body mass, sex, and time since drinking. For medical and forensic specialists.
About this calculator
The Widmark formula calculates blood alcohol concentration (BAC) after alcohol consumption. Proposed by Swedish toxicologist Erik Widmark (1932) and still used in forensic toxicology and medical calculations. Formula. BAC (g/L) = A / (r × m), where A – grams of pure ethanol, r – distribution coefficient (men 0.68-0.73, women 0.55-0.60), m – body mass in kg. With time: BAC at t hours = initial BAC – β × t, where β – elimination rate (0.1-0.2 g/L/hour, average 0.15). Example. An 80 kg man drinks 500 mL of 12% wine (about 47 g ethanol). Initial BAC ≈ 47 / (0.7 × 80) = 0.84 g/L = 0.84 per mille. After 4 hours – 0.84 – 0.15 × 4 = 0.24 per mille. Clinical effects by BAC. <0.5 per mille – minimal impairment, legal driving threshold in most countries. 0.5-1 – impaired coordination, slowed reactions. 1-2 – noticeable ataxia, emotional lability. 2-3 – pronounced ataxia, vomiting. 3-4 – stupor, aspiration risk. >4 – coma, respiratory depression, mortality risk. Chronic alcoholics shift all thresholds with tolerance. Clinical use. Expected BAC calculation in intoxication forecasting. In emergency medicine BAC is measured directly (blood gas chromatography, breath test) – the formula is a reference. In forensic context for BAC at the time of an event (back calculation), Widmark's formula with individual adjustments is applied. Limitations. Substantial individual variability of r and β (10-20%). Absorption rate depends on food in stomach, beverage type, individual ADH/ALDH enzymatic activity (Asian flush in patients with ALDH2*2 polymorphism). In chronic alcoholics β is higher (up to 0.2-0.3), lower in non-drinkers. Does not capture first-pass metabolism (10-20% of ethanol is metabolized in the stomach in men, less in women – one reason for gender differences in BAC).
Source
Formula version: widmark-1932-v1
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