Blood Alcohol Content Calculator (Widmark)
This blood alcohol content calculator gives you a rough estimate of the alcohol concentration in your bloodstream using the classic Widmark formula. Enter your body weight, your sex, the volume of the drink in milliliters, its alcohol strength as a percentage (ABV) and how many hours have passed since you started drinking, and it instantly returns an estimated BAC expressed both in grams per liter (g/L) and as a percentage. It is a useful educational tool to understand how factors like body mass, drink size and elapsed time influence intoxication, but the number it shows should never be treated as a precise or legally reliable measurement.
Estimated blood alcohol (g/L)
Concentration (% BAC)
Rough estimate based on the Widmark formula. It is for orientation only: real blood alcohol depends on countless individual factors (metabolism, food, medication, hydration, liver health, drinking pace) that vary enormously from one person to another. NEVER use this result to decide whether you can drive. If you drink, do not drive.
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How it works
The Widmark equation estimates blood alcohol as C = A / (r · W) − β · t. First the calculator works out A, the grams of pure alcohol you drank: volume in ml × ABV/100 × 0.789 (0.789 g/ml is the density of ethanol). W is your body weight in kilograms and r is the Widmark distribution factor, roughly 0.68 for men and 0.55 for women, reflecting the lower proportion of body water on average. Dividing A by (r · W) gives the peak concentration in g/L. The body then eliminates alcohol at an average rate β of about 0.15 g/L per hour, so we subtract β · t for the hours elapsed. The result is clamped at zero because BAC cannot be negative.
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Preguntas frecuentes
- What is blood alcohol content (BAC)?
- BAC is a measure of how much alcohol is present in your bloodstream. It is commonly expressed in grams of alcohol per liter of blood (g/L) or as a percentage — for example 0.5 g/L equals 0.05%. The higher the BAC, the stronger the effects of alcohol on coordination, judgement and reaction time.
- What is the legal driving limit?
- It varies widely by country. Many nations set the limit at 0.5 g/L (0.05%), some use 0.8 g/L (0.08%), and others have zero-tolerance or 0.2 g/L rules, especially for new or professional drivers. This calculator does not know your local law, so always check the official limit where you are — and remember that impairment starts below any legal threshold.
- How long does it take to sober up?
- The body eliminates alcohol at roughly 0.15 g/L per hour, and nothing reliably speeds that up — not coffee, cold showers or fresh air. So if your BAC peaks at 0.9 g/L it could take around six hours to return to zero. Only time lowers your BAC.
- How accurate is this Widmark estimate?
- It is a rough approximation. The Widmark formula uses average constants that ignore your individual metabolism, whether you ate, your hydration, medications, liver health and drinking pace. Real BAC can be significantly higher or lower than the figure shown, so never rely on it for any decision that matters.
- Can I use this to decide whether to drive?
- No. Absolutely never. This tool is for education and curiosity only. If you have been drinking, the only safe choice is not to drive at all — use a taxi, rideshare, public transport or a sober driver. No calculator can guarantee you are under a legal limit or safe to drive.