BAC Calculator — Blood Alcohol Content
The Widmark formula estimates your blood alcohol concentration (BAC) from the number of standard drinks consumed, your body weight, sex, and how long ago you started drinking. See where your BAC sits against common legal limits and how long until you reach 0.00 %.
kg
Sexo
h
Blood Alcohol Concentration after estimated elimination — Widmark formula
- 1
Ethanol consumed
2 drinks × 14 g/drink = 281 US standard drink = 14 g pure ethanol. - 2
Body water mass (W × r)
70 kg × 1000 × 0,68 = 47.600 - 3
Peak BAC
(28 ÷ 47.600) × 100 = 0,059 - 4
BAC after elimination
0,059 − 0,015 × 1 hrs = 0,044
Como esta calculadora funciona?
BAC (%) ≈ [drinks × 14 g ÷ (body weight in g × Widmark r)] × 100 − 0.015 × hours. The Widmark factor r is 0.68 for men, 0.55 for women. The liver eliminates roughly 0.015 % per hour. This is an estimate — do not rely on it to judge fitness to drive.
Fórmula
How this is calculated
The Widmark formula (developed by Erik Widmark in the 1930s) models blood alcohol as a two-step process. First, the alcohol absorbed into the bloodstream is distributed through the body's water-containing tissues: BAC₀ = (A / (W × r)) × 100, where A is grams of ethanol consumed (1 US standard drink = 14 g), W is body weight in grams, and r is the Widmark factor — approximately 0.68 for men and 0.55 for women, reflecting that women have proportionally less body water. This gives the peak BAC shortly after drinking ceases.
Second, the liver oxidises ethanol at a roughly constant rate of about 0.015 g/dL per hour (range: 0.010–0.020 across individuals). Subtracting the amount eliminated by the time elapsed gives the current estimated BAC. The calculator clamps the result at 0 — you cannot have a negative BAC.
Important limitations: the formula assumes complete absorption (takes 30–90 minutes), average elimination (varies with liver health, food intake, medications), and that the "standard drink" definition matches the one used here (14 g ethanol). The estimate is a guide, not a substitute for a police-grade breathalyser or blood test. Legal BAC limits vary by country and activity — 0.05 % in much of Europe, 0.08 % in the US, UK, and Australia for car drivers, and 0.00 % for professional drivers in many jurisdictions.
Perguntas frequentes
Women generally have a lower Widmark r factor (0.55 vs 0.68 for men) because they have a higher proportion of body fat relative to water. Since alcohol distributes through body water, less water means less dilution and a higher concentration per gram of alcohol consumed.
On average, the liver clears about 0.015 % BAC per hour. Divide your BAC by 0.015 to get an estimate. A BAC of 0.08 % takes roughly 5–6 hours to eliminate entirely. Food, sleep, water and coffee do not meaningfully speed up elimination.
Definitions vary by country. In the US, one standard drink contains 14 g of pure ethanol — roughly 355 ml regular beer (5 %), 148 ml wine (12 %), or 44 ml spirits (40 %). In the UK a "unit" is 10 ml (8 g) of ethanol, and in Australia it is 10 g. Adjust your drink count accordingly.
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TG we-Calculate Editorial Team. (2026). BAC Calculator — Blood Alcohol Content [Online calculator]. TG we-Calculate. https://we-calculate.com/pt/calculator/bac-calculator
TG we-Calculate Editorial Team. "BAC Calculator — Blood Alcohol Content." TG we-Calculate. 2026. https://we-calculate.com/pt/calculator/bac-calculator.
TG we-Calculate Editorial Team, "BAC Calculator — Blood Alcohol Content," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/pt/calculator/bac-calculator
@misc{wecalculate_bac_calculator, title = {BAC Calculator — Blood Alcohol Content}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/pt/calculator/bac-calculator}}, year = {2026}, note = {TG we-Calculate} }
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