How to Use
- Enter body info
Input your body weight and select your gender.
- Enter drink details
Select the type and amount of alcohol consumed, and the hours elapsed since drinking.
- View results
Click Calculate to see your estimated BAC and whether it exceeds legal limits.
What Is Blood Alcohol Concentration (BAC)?
Blood Alcohol Concentration (BAC) is the amount of pure alcohol dissolved in your blood, expressed as a percentage. A BAC of 0.05% means there are 0.05 grams of alcohol per 100 ml of blood. Drinking the same amount produces a higher concentration in people who weigh less or have a lower proportion of body water.
Why It Matters
- Legal limits: In many places driving is an offence above a set BAC, and the measured value determines penalties and licence consequences.
- Physical effects: As BAC rises, judgement, reaction time and motor coordination deteriorate step by step.
This calculator takes the volume and strength of what you drank, your weight and the elapsed time, then uses the Widmark formula to estimate your current BAC and how long it will take to clear. It cannot replace an actual breath or blood test, but it serves as a reference for gauging whether you may be fit to drive after drinking.
The Formula
BAC is estimated with the Widmark formula.
BAC(%) = (A x 5.14) / (W x r) - 0.015 x H
- A = pure alcohol (oz). First find it in grams, then convert: drink volume (ml) x ABV (%) x 0.789 (alcohol density) / 28.35
- W = body weight (lb) = weight (kg) x 2.205
- r = body-water distribution ratio (0.68 for men, 0.55 for women)
- 0.015 = hourly BAC elimination rate, H = hours since drinking
Example: A 70 kg man drinks 360 ml of soju (16.5%) and one hour passes → about 46.9 g of alcohol ≈ 1.65 oz, BAC = (1.65 x 5.14) / (70 x 2.205 x 0.68) - 0.015 x 1 ≈ 0.066%, which falls in the licence-suspension range.