Blood Alcohol Content (BAC) Calculator
Enter sex, weight, number of drinks and hours elapsed to estimate blood alcohol concentration (%) with the Widmark formula.
Input Data
Results
At a glance:Widmark: alcohol(g) = drinks * 14; body-water factor r = male 0.68 / female 0.55. BAC(g/L) = alcohol(g) / (weight(kg) * r) - 0.15 * hours; BAC(%) = BAC(g/L) / 10. Negative results are shown as 0.
Formula
alcoholG = drinks * 14.
bacGperL = alcoholG / (weightKg * r) - 0.15 * hours.
bac% = max(0, bacGperL) / 10.
How to Use
- Enter sex, weight, number of drinks and hours since the first drink.
- Get the estimated blood alcohol concentration (%).
Case Studies
70kg male, 3 drinks, 2 hours
alcoholG = 42; bacGperL = 42/(70*0.68) - 0.3 = 0.882 - 0.3 = 0.582; BAC ~ 0.058%.
FAQ
Is this accurate?
It is a rough estimate; actual BAC varies with food, metabolism and drink type. Legal limits use breath/blood testing.
What is one drink?
This tool uses 1 drink = 14g pure alcohol (~350mL 5% beer / 150mL 12% wine / 45mL 40% spirit).
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References
Content reviewed by the Calculatorism editorial team. Results are for reference only; please refer to the relevant authorities for the official figures.