BAC (Blood Alcohol Content) Calculator
Estimate your blood alcohol content based on weight, gender, number of drinks, and time spent drinking.
Always drink responsibly.
Blood Alcohol Content (BAC) estimates the concentration of alcohol in the bloodstream, expressed as grams of alcohol per 100 mL of blood (%).
Widmark formula:
BAC = (Alcohol in grams / (Body Weight in grams × r)) − (0.015 × Hours since drinking began)
Where r is the Widmark distribution factor:
- Male: r = 0.68 (men distribute alcohol through a larger lean body water volume)
- Female: r = 0.55 (women have proportionally more body fat, less body water)
Alcohol content of standard drinks: One standard drink ≈ 14 grams of pure alcohol:
- 12 oz beer at 5% ABV = 14.2 g
- 5 oz wine at 12% ABV = 14.2 g
- 1.5 oz spirits at 40% ABV = 14.2 g
Elimination rate: The liver metabolizes alcohol at approximately 0.015% BAC per hour (roughly one standard drink per hour for an average adult).
Worked example:
Male, 80 kg (80,000 g), drinks 3 standard drinks (42 g alcohol) over 1 hour.
BAC = (42 / (80,000 × 0.68)) − (0.015 × 1)
BAC = (42 / 54,400) − 0.015
BAC = 0.0772% − 0.015% = 0.062%
Estimated BAC: 0.062% — below the 0.08% legal limit in most US states, but impairment begins at 0.02–0.05%.
BAC level effects:
- 0.02%: Mild relaxation, slight mood change
- 0.05%: Reduced inhibitions, impaired judgment
- 0.08%: Legal limit in most US/EU countries
- 0.15%: Significant impairment; nausea common
- 0.30%+: Life-threatening; medical emergency
DISCLAIMER: This is an estimate only. Individual metabolism, food intake, medications, and tolerance vary widely. Never drive after drinking.