Blood Alcohol Content Calculator

Get a rough estimate of your blood alcohol content based on weight, gender, number of drinks and time, using the Widmark formula.

Estimated BAC
0.62 ‰
Above Norway's driving limit (0.2 ‰)
Elimination rate
0.15 ‰/hour
Back to zero in approx.
4.1 hours
Embed on your website →

How to use the BAC calculator

  1. Choose your gender and enter your weight.
  2. Enter the number of standard drinks you've had (1 drink ≈ 1 glass of wine, 1 bottle of beer, or 1 shot of spirits).
  3. Enter how many hours it's been since you started drinking. The calculator shows an estimate of your BAC.

How the BAC is calculated

The calculator uses the Widmark formula, a classic method for estimating blood alcohol concentration:

BAC = (Alcohol in grams ÷ (weight × r)) − (0.15 × hours)
r = 0.68 for men, 0.55 for women — 1 drink ≈ 12 g of pure alcohol

The formula accounts for the fact that alcohol distributes differently in the body depending on gender (the r factor), and that the body breaks down alcohol at a fairly steady rate of around 0.15 ‰ per hour. The result is only a mathematical estimate — actual BAC is also affected by stomach contents, drinking pace and individual differences in metabolism.

Important: This is only a rough mathematical estimate and must never be used to decide whether it's safe to drive or perform other activities that require sobriety. Actual BAC can differ significantly from the calculation. Norway's legal driving limit is 0.2 ‰ — one of the strictest in the world; many other countries use 0.5 ‰ or 0.8 ‰. Never drive after drinking alcohol, regardless of what the calculation shows or which country you're in — always choose a safe way home instead.
Ad space — reserved for future partners (e.g. taxi/transport, non-alcoholic alternatives)

Frequently asked questions

How accurate is this calculator?

The Widmark formula gives only a rough estimate. Actual BAC is affected by stomach contents, drinking pace, medication and individual differences, and can therefore deviate from the calculated result in either direction.

What's Norway's legal driving limit?

Norway's legal driving limit is 0.2 ‰, among the strictest in the world. Since this calculator only gives an estimate, you should never drive after drinking alcohol, no matter what the calculation shows.

How much is one standard drink?

One standard drink corresponds to roughly 12 grams of pure alcohol — for example a bottle of beer (33 cl, 4.5 %), a glass of wine (12 cl, 12 %) or a shot of spirits (4 cl).

Embed this calculator on your website

Copy the code below to show this calculator directly on your blog or website — completely free.