BAC Calculator

The Blood Alcohol Concentration Calculator provides an accurate estimate of your current blood alcohol concentration based on several key inputs and personal characteristics.

Amount of Alcohol Consumed

There was an error with your calculation.

Blood Alcohol Content (BAC)

BAC is around 0.039%
It will take around 2.6 more hours to reach 0%

Table of Contents

  1. The Ultimate Guide to the Blood Alcohol Concentration Calculator
  2. What a Blood Alcohol Concentration Calculator is
  3. How a Blood Alcohol Concentration Calculator Works
  4. Example
  5. Tips For Staying Within the Safe Limits of Blood Alcohol Concentration
  6. Don’t Drink and Drive
  7. Understand Your Own Limits
  8. Understand the Definition of “One Drink”

The Ultimate Guide to the Blood Alcohol Concentration Calculator

Those of legal age who are drinking recreationally do not often seek out their blood alcohol concentration levels. After all, the primary purpose of consuming alcohol is to become somewhat disinhibited.

Developing a habit, or at least being aware of your BAC levels based on the amount of alcohol you consume, can be very helpful, especially if you plan to get behind the wheel after a few drinks.

If you’re indulging in alcohol, driving should be, unquestionably, avoided, for it not only puts you in danger but those around you in danger; not to mention, it’s against the law to drive impaired.

One way to somewhat accurately measure your blood alcohol concentration levels is by using an online BAC calculator.

With that said, in what follows, we’ll define a blood alcohol concentration, how the blood alcohol concentration calculator works, what problems it solves, and why you, the user, can benefit from its function. So, if you’re ready to ensure that you remain under the legal limits of blood alcohol concentration, this article is for you.

Continue reading to learn more.

What a Blood Alcohol Concentration Calculator is

Before defining a blood alcohol concentration calculator, it’s crucial to determine your blood alcohol concentration.

Blood alcohol concentration is used to identify how intoxicated and inebriated someone is. The measurement is typically expressed as a percentage of the volume of alcohol found in the blood at the time of measurement.

In the U.S., the legal limit for blood alcohol concentration (BAC) while driving is typically 0.08%. Driving with a BAC exceeding this limit is prohibited in all states. BAC is measured as the number of grams of alcohol per 100 milliliters of blood. For example, a BAC of 0.08% means there are 0.08 grams of alcohol per 100 milliliters of blood.

A Blood Alcohol Concentration Calculator is a mechanism, resource, or tool used to derive an accurate BAC percentage based on several required inputs.

The inputs involved with the Blood Alcohol Concentration Calculator include the following:

  • Gender;
  • Body Weight;
  • Time Since Your First Drink;
  • The Amount of Alcohol Consumed;
  • The Type of Alcohol Consumed;
  • ABV% of each type of alcoholic beverage you’ve consumed.

While individuals may know the quantity of alcohol they consume, such as the volume in a standard beer or wine glass, they might not always be aware of how this translates into blood alcohol concentration (BAC). BAC calculators require exact measurements to provide accurate estimates, which necessitates precise knowledge of alcohol volume and content.

Law enforcement does not use online BAC calculators when assessing drivers for impairment. Instead, they employ professionally calibrated devices known as breathalyzers, which provide immediate and legally admissible BAC levels.

Online BAC calculators, however, can serve as educational resources. They help individuals estimate their BAC based on their alcohol intake, offering insight into how alcohol affects their body and informing safer drinking decisions.

How a Blood Alcohol Concentration Calculator Works

Wondering how to calculate your blood alcohol concentration, but unsure where to start? Luckily, it’s pretty simple, especially when you use the free blood alcohol concentration calculator.

As mentioned, the BAC calculator requires the user to input several pieces of basic information regarding personal characteristics (gender and body weight) and factors related to alcohol consumption (amount of alcohol consumed, etc.).

Based on the relative inputs, the calculator uses algorithms to calculate and derive a real-time measurement of an individual’s BAC. Provided in a singular percentage (ex. 0.05%), the BAC calculator is an effective alternative for those curious to know how intoxicated they are or may become.

To further illustrate how to use the BAC calculator and in what context it’s to be used, consider the following practical example of an individual seeking to know whether three drinks is too much to get behind the wheel and drive.


John, a 35-year-old man, attends a wedding reception where he enjoys some drinks during the evening. He is aware of the dangers of drinking and driving and has made a personal limit of two drinks to ensure he stays well below the legal limit before he considers driving. He also plans to wait a significant amount of time after his last drink before leaving.

Throughout the night, he tracks his consumption: two glasses of wine over the course of the first two hours. Before even considering whether he might drive at the end of the evening, John decides to use an online BAC calculator to estimate his blood alcohol concentration as a way to reinforce his decision to drink responsibly.

He inputs his gender, weight, the type and quantity of alcohol consumed, and the time over which he consumed his drinks. The calculator estimates that his BAC should be below the legal limit by the time he plans to leave, but this is only an estimate.

John knows the calculator doesn't account for individual factors such as his metabolism, recent food intake, or how his body processes alcohol. With this in mind, he uses the calculator as a general guide and not as a definitive measure of his ability to drive. He decides to wait an additional hour and drink water to ensure his body has time to metabolize the alcohol.

In the end, even though the calculator indicated he might be legally safe to drive, John chooses to take a taxi home instead. He understands that the calculator's estimate isn't foolproof and that the safest option is to not drive at all after drinking.

Tips For Staying Within the Safe Limits of Blood Alcohol Concentration

If you decide to drive, the desire not to exceed the legal limit of blood alcohol concentration is important both for your safety and for the safety of others.

To stay below the legal limits, you need to drink responsibly and have a better understanding of what it takes to reach the statutory BAC limit.

With that said, the following are a few helpful insights and tips on how to remain under the legal BAC limit while still enjoying a drink or two with friends. Some of these tips involve explicitly measuring your own BAC levels.

Don’t Drink and Drive

Why is it first on the list? It is not just advice or a recommendation, but a law introduced to keep citizens who drink alcohol safe from the risk of traffic accidents.

If you choose to drink over the recommended amounts that would otherwise keep your blood alcohol concentration at a safe and legal level, plan and act accordingly; book a cab home, find a designated driver, etc.

Whatever you do, don’t step behind the wheel.

Understand Your Own Limits

Everyone metabolizes alcohol differently, and several factors influence this process beyond just weight and sex, including genetics, health, and individual tolerance levels. A 150-pound female typically will not process alcohol the same way as a 215-pound male, and the effects can vary widely even among people of the same weight and gender.

Relying solely on weight and gender, as suggested by some online calculators or measurement charts, oversimplifies the complexity of alcohol metabolism. These tools may offer a basic guide, but they cannot account for all personal factors that affect your BAC. Furthermore, it's crucial to understand that the ability to legally drive should not be determined by BAC estimates alone. Even if you are under the legal limit, your driving could still be impaired. The safest approach is to avoid driving after drinking any amount of alcohol.

Understand the Definition of “One Drink”

Finally, understanding the definition of "one drink" is imperative to remaining under the legal BAC limit. Failure to clearly define these parameters will only result in you mistakenly over-consuming alcohol, thus increasing the likelihood of breaking the law should you decide to drive.

Health professionals define “one drink” as the following:

  • 12 ounces of beer (5% ABV) or about 350 ml;
  • 8 ounces of malt liquor (7% ABV) or about 240 ml;
  • 5 ounces of wine (12% ABV) or about 150 ml;
  • 1.5 ounces of distilled spirits (40% ABV) or about 40 ml.

By using this as a guide, you inevitably set yourself up for success in avoiding exceeding the legal limit of blood alcohol concentration when driving.