Alcohol Metabolism & BAC Calculator
Estimate your blood alcohol content with the Widmark formula and see how many hours it takes to get sober and safe to drive.
Drinking Profile
Number Format Region
Biological Sex (Widmark r factor)
Body Weight Unit
Body weight is clamped to a minimum of 80 lbs and elapsed time to 0 hours, so the Widmark division can never hit zero and BAC can never fall below 0.000 %.
Metabolism Breakdown
Hourly Sobriety Timeline
Each row removes a further 0.015 % BAC, the average hepatic elimination rate. The descent is linear, so nothing but elapsed time moves it faster.
Legal disclaimer: this tool is a mathematical estimation based on the Widmark formula and population averages. It is not a breathalyzer, not a medical device and not evidence of fitness to drive. Actual blood alcohol content varies with food, medication, body composition, health and genetics. Never use this result to decide whether to drive or operate machinery, and never let it override a professional breathalyzer reading or medical advice.
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What is the mathematical Widmark formula for calculating blood alcohol concentration levels accurately?
Erik Widmark published the working model of alcohol distribution in 1932 and it remains the backbone of every forensic and consumer BAC estimate today. Alcohol dissolves only into body water, so the equation divides the mass of ethanol consumed by body mass multiplied by a distribution ratio, then subtracts the alcohol the liver has already oxidised in the time since the first drink. This calculator implements the full chain from fluid ounces of a beverage all the way down to grams of ethanol, so a 16 oz craft IPA is never silently treated as a single standard drink.
Ethanol per drink (g) = oz x 29.5735 mL x (ABV / 100) x 0.789 g/mL Total ethanol (g) = ethanol per drink x number of drinks Standard drinks = total ethanol / 14 g Body weight (g) = kg x 1000 (lbs / 2.2046 x 1000) r factor = 0.68 male / 0.55 female Peak BAC % = (total ethanol / (weight g x r)) x 100 Current BAC % = max(0, peak BAC - 0.015 x hours elapsed) Hours to 0.00 % = current BAC / 0.015 Hours to drive (0.02) = max(0, (current BAC - 0.02) / 0.015)
How many hours does it take for three standard beers to clear your system based on your body weight?
Elimination is linear, not proportional, which is the single most counter-intuitive fact about alcohol metabolism. The liver oxidises roughly 0.015 percentage points of BAC per hour whether you are at 0.03 % or 0.18 %, so doubling the peak doubles the wait. Three standard beers put a 180 lb male near 0.086 % at peak, which needs about 5.7 hours to reach zero. The same three beers put a 140 lb female near 0.137 %, requiring roughly 9.1 hours. Nothing shortens that clock: coffee, showers, food after the fact and exercise all leave the elimination rate untouched while making a drinker feel deceptively alert.
What is the average peak BAC for each body weight bracket against the number of standard drinks consumed?
The grid below shows peak BAC immediately after drinking, before any metabolic burn-off, using the male distribution factor of 0.68 and US standard drinks of 14 g ethanol each. Cells at or above 0.08 % are the per-se DUI threshold in 49 states. Female readers should scale each figure up by roughly 24 % to account for the 0.55 distribution factor.
| Body weight | 1 drink | 2 drinks | 3 drinks | 4 drinks | 5 drinks | 6 drinks |
|---|---|---|---|---|---|---|
| 120 lbs | 0.038 % | 0.076 % | 0.113 % | 0.151 % | 0.189 % | 0.227 % |
| 140 lbs | 0.032 % | 0.065 % | 0.097 % | 0.130 % | 0.162 % | 0.195 % |
| 160 lbs | 0.028 % | 0.057 % | 0.085 % | 0.113 % | 0.142 % | 0.170 % |
| 180 lbs | 0.025 % | 0.050 % | 0.076 % | 0.101 % | 0.126 % | 0.151 % |
| 200 lbs | 0.023 % | 0.045 % | 0.068 % | 0.091 % | 0.113 % | 0.136 % |
| 220 lbs | 0.021 % | 0.041 % | 0.062 % | 0.083 % | 0.103 % | 0.124 % |
| 260 lbs | 0.017 % | 0.035 % | 0.052 % | 0.070 % | 0.087 % | 0.105 % |
How do you convert a large craft beer or a double pour of wine into US standard drink equivalents?
Multiply the volume in fluid ounces by the ABV percentage and divide by 0.6, because a US standard drink contains 0.6 fl oz of pure alcohol. A 16 oz IPA at 7 % is (16 × 0.07) / 0.6 = 1.87 standard drinks. A generous 9 oz pour of 14 % red wine is 2.1 standard drinks, nearly double what the drinker counted. This is the most common reason a self-reported "three drinks" produces a breathalyzer reading far above expectation.
Why does gender change the Widmark r factor and how much higher does a woman's BAC actually go?
The r factor is the fraction of body mass available as water for alcohol to dissolve into. Population averages put that near 0.68 for men and 0.55 for women, driven mainly by differences in lean mass and total body water. Because r sits in the denominator, the lower value raises BAC by roughly 24 % at identical weight and dose. Lower gastric alcohol dehydrogenase activity in women lets more ethanol reach the bloodstream before first-pass metabolism, pushing the practical gap slightly wider still.
Is a calculated Widmark estimate ever a safe substitute for a breathalyzer before deciding to drive home?
No. The model assumes complete absorption, an average body composition, an average elimination rate and an empty stomach correction that does not exist. Real readings routinely differ by 0.02 % or more, and impairment charges do not require crossing 0.08 %. Treat every figure here as educational, plan a ride in advance, and let time — never a calculator — be the thing that decides you are sober.