Have you ever wondered how to calculate or at least estimate your blood alcohol concentration, or BAC, after having a few drinks with your friends? How can you do it if you don’t have a breathalyzer with you ?.
Well, here is the formula to estimate your BAC. It is called the Widmark Fomula.
BAC = [Alcohol consumed in grams / (Body weight in grams x r)] x 100
“r” is the gender constant and is equal to 0.55 for a woman and 0.68 for a man
But how do you know how much alcohol you consumed?
Well, that is easy.
Alcohol consumed in grams = Volume in mL * % of alcohol in the beverage * 0.789 g/mL
Let’s do an example.
You are a man. (r = 0.68)
Your weight is 80 Kg = 80’000 g
You drank 3 cans (3*375 mL) of beer (4% = 0.04) while watching soccer.
What is your BAC?
3*375 mL* 0.04 * 0.789 g/mL / (80’000 g * 0.68) * 100 = 0.06
What if you drink a whole bottle of 700 mL Vodka (45% = 0.45)
700 mL* 0.45 * 0.789 g/mL / (80’000 g * 0.68) * 100 = 0.46
In case you use imperial units, you can easily convert :
1 fl. Oz = 29.6 mL
1 pound = 454 g
If you’re not much for math, you can also use one of the numerous websites that help you find out your BAC.