Blood Alcohol Content (BAC)

blood alcohol content bac

Blood Alcohol Content (BAC) measures the level of alcohol in your bloodstream as a percent of your blood that is concentrated with alcohol. When you drink alcohol, it gets processed by your liver. Your liver can roughly process one drink per hour. If you drink faster than your liver can process the alcohol, you will start to feel the effects of intoxication.

How Blood Alcohol Levels Are Measured

There are a few ways of calculating BAC. The most accurate measurement can be obtained only by drawing a sample of blood. However, breathalyzers can provide pretty reliable estimates. Accurate Breathalyzers take a sample of alveolar (deep lung) air. They are considered reliable enough to be used as legal evidence in courts over the world.

However, many police departments use handheld breathalyzers. These are less accurate and are not considered legal evidence of intoxication. The reason police departments still use them is to determine probable cause. If they find a high enough BAC level using a handheld breathalyzer, they can obtain a blood sample to get an accurate reading.

What Affects Your Blood Alcohol Content

There are many factors that can affect your blood alcohol level, such as your size, gender, and physical condition. Other factors include what you have had to eat, how much you have slept, and what medications you are on. One of the most important factors is the actual alcohol content of your “drink.”

Blood Alcohol Content Chart For Men

Approximate Blood Alcohol Percentage
DrinksBody Weight in Pounds
100120140160180200220240
0.00.00.00.00.00.00.00.00Only Safe Driving Limit
1.04.03.03.02.02.02.02.02Driving Skills
Significantly Affected


Possible Criminal
Penalties

2.08.06.05.05.04.04.03.03
3.11.09.08.07.06.06.05.05
4.15.12.11.09.08.08.07.06
5.19.16.13.12.11.09.09.08
6.23.19.16.14.13.11.10.09Legally Intoxicated


Criminal Penalties

7.26.22.19.16.15.13.12.11
8.30.25.21.19.17.15.14.13
9.34.28.24.21.19.17.15.14
10.38.31.27.23.21.19.17.16Death Possible
Subtract .01% for each 40 minutes of drinking.
One drink is 1.25 oz. of 80 proof liquor, 12 oz. of beer, or 5 oz. of table wine.

Blood Alcohol Content Chart For Women

Approximate Blood Alcohol Percentage
DrinksBody Weight in Pounds
90100120140160180200220240
0.00.00.00.00.00.00.00.00.00Only Safe Driving Limit
1.05.05.04.03.03.03.02.02.02Driving Skills
Significantly Affected


Possible Criminal
Penalties

2.10.09.08.07.06.05.05.04.04
3.15.14.11.10.09.08.07.06.06
4.20.18.15.13.11.10.09.08.08
5.25.23.19.16.14.13.11.10.09
6.30.27.23.19.17.15.14.12.11Legally Intoxicated


Criminal Penalties

7.35.32.27.23.20.18.16.14.13
8.40.36.30.26.23.20.18.17.15
9.45.41.34.29.26.23.20.19.17
10.51.45.38.32.28.25.23.21.19
Death Possible
Subtract .01% for each 40 minutes of drinking.
One drink is 1.25 oz. of 80 proof liquor, 12 oz. of beer, or 5 oz. of table wine.

AwareAwakeAlive has a pretty neat BAC Calculator that you can punch in your numbers to determine your BAC.

How Blood Alcohol Content Affects Your Driving Ability

Alcohol can negatively impact many of your senses after only one drink, but legally a blood alcohol content (BAC) level of 0.08 percent means impaired.

  • BAC of 0.02 is significantly lower than the 0.08, but a person may still experience a lack of judgment. There may also be increased feelings of relaxation, a rise in body temperature, increased mood swings, impaired vision, and the inability to multi-task.
  • BAC of 0.05 is another level where the person experiences a lack of judgment, but it is accompanied by exaggerated behavior, impaired coordination, lack of motion detection, alertness, decreased muscle control, and delayed response time.
  • BAC of 0.08 is the legally impaired limit. A person may experience a reduction in muscle coordination, little to no judgment, impaired reasoning, lack of speed control and, and inability to process information.
  • BAC of 0.10 is one step above the legal limit of DUI and DWI. A person may show poor coordination, reduced reaction times, inability to control their vehicle, and slurred speech.
  • BAC of 0.15 is even further past the legal is when there may extreme loss of balance, virtually no muscle control, vomiting, impaired vision, and hearing. The attention span is reduced, which also makes it almost impossible to drive.
  • BAC of 0.40 or higher is extremely dangerous. You may be at serious risk for coma or death.

The Effects of Alcohol

  1. Judgment – since alcohol affects our mental functions first, we quickly lose the ability to make sound and responsible decisions.
  2. Concentration – alcohol impairs the driver’s ability to concentrate on multiple tasks such as vehicle speed, the position of the vehicle, other traffic on the road, turning the radio, and participating in a conversation with passengers.
  3. Comprehension – we see a reduced ability to interpret signs and signals. This results in drivers unable to respond quickly to emergency situations or not following the rules of the road (such as not stopping at red lights).
  4. Motor Skills – the loss of coordination slows down our reaction time and even the ability to react.
  5. Vision & Hearing – both senses are key to driving safely. Shockingly, alcohol reduces visual acuity by up to 32%! Drivers can lose their depth perception and ability to judge distances. On the hearing side, drivers may not understand which directions sounds are coming from or may misinterpret their meaning.
  6. Reaction Time – driving requires a lot of concentration as it is. When alcohol slows down your reaction time by 15-25%, preventable car crashes become unavoidable.

Read our post on the drunk driving statistics to learn about the dangers of drinking and driving.

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