What is a Blood Alcohol Content Calculator?

Feb 15, 2017

It’s often easy to go out for a few drinks with friends or coworkers and lose track of how many you’ve had over a period of time. At some point, you may try to do the math in your head to figure out if you’re safe to drive home, but chances are, it’s already too late. The best way to be safe is to plan ahead on how you will be getting home at the end of the night, but a good way to keep track of what you’ve had to drink is a blood alcohol content calculator, or blood alcohol content chart. First, we’ll dive into what BAC is and how it is associated with drinking.

What is BAC?

BAC refers to blood alcohol content, which is used to measure a person’s level of alcohol intoxication. The estimate of a person’s BAC can be used for legal and medical procedures and is found through either a blood, urine, or breath test.

A person’s BAC is expressed as a percentage of blood that is concentrated with alcohol, which is why BAC also sometimes represents blood alcohol concentration. You are legally intoxicated in the United States if your BAC is 0.08 percent or higher, which is eight units of alcohol per 1,000 units of blood, meaning our bloodstream is composed of .08 percent alcohol.

This might not seem like a lot, but alcohol begins to affect a person at even lower levels than that. A general rule is the higher a person’s BAC — the higher their impairment.

But how do you find out your BAC? That’s where the BAC calculator comes in.

What is a Blood Alcohol Content Calculator?

A blood alcohol content calculator is a tool used to estimate your blood alcohol levels. It is important to note that we said “estimate” here and not “accurately measure” as there are a lot of factors in play that affect the rate of alcohol absorption in the body that are not considered in the calculation. Some of these factors include metabolism, gender, body fat percentage, underlying health issues, medications you might be taking, how much food is in your stomach, how often you consume alcohol, and more. No blood alcohol content calculator is 100 percent accurate.

However, a blood alcohol content calculator can be useful to give you an idea of what your BAC is based on what you’ve had to drink over a given period of time.

Example of a Blood Alcohol Content Calculator

Here is one such blood alcohol content calculator that uses weight and number of drinks.

While the “one drink per hour” rule is often thought of as the best way to monitor your drinking, the problem is that this doesn’t always work, and is hard to monitor. BAC calculators like this one are free and readily available to use online to help you approximate your BAC levels based on what you’ve had to drink and your weight.

However, blood alcohol content calculators like this only take two parts of a tricky equation (your weight and number of drinks) and make assumptions about the strength of drinks, and don’t take into account many personal factors that play a role in inebriation. Your actual BAC will vary based on these personal factors, and is best measured using a breathalyzer.

What the Chart Readings Mean

Since some numbers and decimal points probably don’t make much sense to anyone, other than being able to see whether or not they are above or below the legal limit of 0.08 percent, let’s take a look at the effects of alcohol at various percentages on the scale.

0.00 – 0.03 – many will feel no impairment at this level, while light drinkers may begin to feel some effects.

0.03 – 0.06 – most will feel slightly impaired and relaxed, with the addition of some mild euphoria and decreased inhibitions.

0.06 – 0.10 – the stage where a person crossed over the legal limit to drive, many people will feel a “buzz” at this level and some moderate impairment of muscle coordination.

0.10 – 0.15 – now the person has become drunk. There will be a noticeable deterioration of the person’s reaction time, slurred speech, impaired movement and balance, and even some nausea.

0.15 – 0.20 – the person may become further nauseous and vomit, and may also experience a “blackout.”

0.20 – 0.30 – a loss of consciousness and bladder control can occur at this level.

0.30 – 0.40 – most likely unconscious, this level has a light risk of causing death.

Above 0.40 – High risk of impaired breathing, coma, and death. 0.45 percent is a fatal dose for most people.


It’s important to remember that a blood alcohol content calculator can only provide a rough estimate for your BAC, and not an accurate reading. For that, purchase a breathalyzer, and always make arrangements for safe rides home when you know you will be exceeding legal limits to drive.

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