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BAC Calculator (Blood Alcohol Content)

Created by Mateusz Mucha, Jack Bowater, Maria Kluziak and Łucja Zaborowska, MD, PhD candidate
Reviewed by Dominik Czernia, PhD
Based on research by
Hustad JT, Carey KB. Using calculations to estimate blood alcohol concentrations for naturally occurring drinking episodes: a validity study.; Journal of Studies on Alcohol and Drugs; January 2005See 1 more source
Peck RC, Gebers MA, Voas RB, Romano E. The relationship between blood alcohol concentration (BAC), age, and crash risk; Journal of Safety Research; May 2008
Last updated: Jan 18, 2024


The BAC Calculator is a tool that can help you assess the concentration of alcohol in your blood. The calculation is based on what kind of alcohol you drank, how much of it you consumed, and how long ago.

As your blood alcohol concentration depends on a variety of aspects, this sobriety calculator takes into consideration your body weight and sex as well. Have you ever considered why one person gets drunk more easily than another? Or wondered how this changes depending on the weight, sex, or type of alcohol? If so, keep reading.

How to use blood alcohol calculator?

To find out what your blood alcohol content actually is, you only need to fill the blanks with the number of beers, wine glasses, and/or vodka shots you drank. Do not ask friends; the calculator can only work with the exact amount that you drank. If you can't, you don't need to assess it; you are certainly drunk. When you have done that, plug in your weight, sex, and the time when you started drinking. The BAC Calculator will estimate the percentage of your blood comprised of alcohol.

Let’s take an example:

  1. Large beers: 3
  2. Wine glasses: 0
  3. Vodka shots: 5
  4. Body weight: 90
  5. Sex: male
  6. Started drinking: 8 hrs ago

The calculator shows your blood as 0.6‰ alcohol.

You can also use the advanced version of the calculator, which contains an additional “raw alcohol” input. You can either fill it with the amount of alcohol you drank, typing it in grams, or fill in the first three blank fields, and the calculator will display your raw blood alcohol content. For our 3 large beers and 5 vodka shots, which we have plugged in, we get 165 grams of raw alcohol.

Why use the drunk calculator?

Sometimes, after drinking alcohol, you feel horrible. If this is the case, then you are still under the influence of alcohol. However, not everyone's hangover is a disaster. In such a situation, you may want to drive home in the morning (or afternoon) but are unsure if the breathalyzer test would show any alcohol content in your blood. That's why you can use the BAC Calculator to measure your blood alcohol concentration before you set off. However, it's worth confirming the result with another tool, like a store-bought breathalyzer test, which can be found in most pharmacies.

You can use the drunk calculator to appease your curiosity or to compare your result with those of your friends. If you are interested in other calculators related to the topic, you should take a look at our BMR calculator and wedding alcohol calculator.

Sobriety calculator

This blood alcohol calculator can not only be used to check the concentration of alcohol in your blood right now but also to estimate when your blood alcohol content is going to equal 0. This is when you're fully sober again — it might be longer than you imagine! This number is presented below your current blood alcohol level. Thanks to this function, you can find out how much time you need to get a particular amount of alcohol out of your system and how it varies depending on the type of drinks you consume.

How BAC affects your behavior

It is good to know how exactly a certain concentration of alcohol affects your organism, especially if you're trying to estimate when it will be okay to drive again.

BAC

Effects

0.02%

Relaxation, slight impairment of visual functions, slight impairment to divided attention.

0.05%

All above and loss of small-muscle control leading to difficulty focusing eyes, impaired judgment, lowered alertness, and reduced coordination.

0.08%

All above plus poor muscle coordination, impaired speech, impaired self-control, reason, and memory.

0.10%

All above and poor coordination, slurred speech, slowed thinking.

0.15%

All above and potential vomiting, major loss of balance.

In conclusion, the BAC calculator can tell you:

  • How drunk you are (regardless of how you feel).
  • How long you need to get back to total sobriety.
  • How the three most common alcohol types affect your blood alcohol content.

🙋 Are you worried about your alcohol consumption pattern? Check if you're an alcoholic with a test developed by WHO in our audit score calculator.

FAQ

What does BAC stand for?

BAC stands for blood alcohol concentration. It quantifies the result of a test to measure the percentage of alcohol in the blood. This level can be determined by a breath test or by chemical tests.

How can I calculate BAC?

You can use the Widmark's formula to calculate BAC:

  1. Determine the amount of alcohol consumed in grams, A.

  2. State your body weight in kilograms, Wt.

  3. Find the ratio of body water to total weight, bw.

  4. Choose a time (t) in hours since alcohol consumption began.

  5. Estimate the metabolism rate (mr): typically, it's 0.017% per hour.

  6. Use the Widmark's formula:

    BAC = A/(bw × Wt) × 100% − mr × t

Which factor is the only way to lower BAC?

The only factor that reduces BAC is spending time without drinking. You need to give your body time to absorb and get rid of the alcohol. Popular beliefs say that coffee, a cold shower, or drinking a glass of water will help you sober up faster, but this is not true.

What BAC means that I am drunk?

You are likely to start feeling the effects of being drunk above 0.08% BAC. At this point, you may experience mild impairment of speech, vision, coordination, and reaction times. This is why in the United States (except Utah) you cannot drive under the influence of alcohol at 0.08% BAC or higher.

Which factors affect BAC levels?

Factors affecting BAC are:

  • Weight — The heavier the person, the lower the BAC;
  • Sex — Men generally metabolize alcohol at a faster rate than women;
  • Medications — Some drugs can interact with alcohol and damage the liver;
  • Speed of sipping — Drink slowly to keep your intoxication under control;
  • Food — Drinking on an empty stomach results in faster alcohol absorption and intoxication; and
  • Number of standard drinks you drank.

What is my BAC after 2 beers?

0.06% or 0.6‰, assuming you are a US man weighing 180 lbs and just had two large beers (50 grams of raw alcohol). You will need 4 hours for your body to metabolize this amount of alcohol.

Mateusz Mucha, Jack Bowater, Maria Kluziak and Łucja Zaborowska, MD, PhD candidate
I am from
USA or Canada
Body weight
lb
Sex
Male
Started drinking
hrs
ago
I drank
large beers
...and
wine glasses
BAC
3
Time until sober
20
hrs
1
min
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