Blood Alcohol (BAC) Calculator
Blood alcohol content from drinks.
Estimated BAC
0%
Enter the amount, alcohol content and your body weight.
What is BAC?
Blood Alcohol Concentration (BAC) is the percentage of alcohol in 100mL of blood, used as a standard for drunk-driving enforcement. This calculator uses the Widmark formula to estimate BAC from the amount consumed, ABV, body weight, and elapsed time.
How it is calculated
Alcohol (g) = volume (mL) × (ABV/100) × 0.789, then BAC(%) = alcohol (g) ÷ (body weight (g) × r) × 100 − 0.015 × hours, where r is 0.68 for men and 0.55 for women (reflecting body water ratio differences).
What the Widmark formula can and cannot tell you
Blood alcohol estimates are computed from the amount drunk, body weight and elapsed time. Individual variation puts real readings above or below the figure, so a result under the limit is never a reason to drive.
How the estimate is built
The Widmark formula divides the pure alcohol consumed by body weight and a distribution coefficient to reach a peak concentration, with the sex coefficient reflecting differences in body water and fat.
Hourly elimination is then subtracted. Rates generally fall between 0.008 and 0.030 percent per hour, and because an average can mislead, investigative practice applies the figure most favourable to the suspect.
Alcohol mass comes from volume multiplied by strength and density, so the same number of glasses at a different strength changes the result — millilitres and ABV matter, glass counts do not.
Why estimates miss
Absorption depends heavily on whether there is food in the stomach — drinking on an empty stomach raises the peak sooner and higher, and carbonated drinks speed it further.
Elimination varies between people. Genetic differences in alcohol-metabolising enzymes, liver function and habitual drinking can separate hourly rates several-fold, and medication can shift them again.
Pace and the timing of the last drink matter too: absorption continues after a session ends, so the level can still be rising — and after a heavy night, sleep does not guarantee a reading below the limit.
Limits and penalties
Korean road traffic law treats 0.03 percent as the threshold for driving under the influence: 0.03 to below 0.08 draws licence suspension, and 0.08 or above revocation.
Refusing a test is itself an offence, injuring someone while over the limit brings aggravated penalties under separate legislation, and repeat offences are punished more severely.
Roadside breath testing measures an actual value rather than an estimate; a driver who disputes it may request a blood test, which takes precedence.
Legal basis
- Threshold for intoxicated driving — Road Traffic Act art. 44
- Penalties — Road Traffic Act art. 148-2
- Dangerous driving causing injury or death — Act on Special Cases Concerning the Punishment of Specific Crimes art. 5-11
- Estimation method — Widmark formula, as applied in investigative practice