Best Online BAC Calculators

Florida law has created a version of DUI based solely upon a person’s BAC at the time of driving (DUBAL). In a DUBAL case, the legal driving limit in the State of Florida is 0.08%.

For this reason, DUI defense attorneys, prosecutors, and expert witnesses often have the task of trying to determine a person’s BAC at the time of driving using all of the available evidence.

The State of Florida has lower legal BAC limits for some types of drivers, including drivers who are:

  1. under 21 years old; or
  2. driving a commercial motor vehicle.

Although in some states, the “per se” version of DUI will also consider a BAC taken within a certain of period of time after driving, Florida law looks only at the BAC level at the time of the test as a way to estimate the BAC at the time of driving.

The longer the length of time between the two events, the harder it is to extrapolate backward. To complicate matters, the BAC will increase, plateau, and then decrease over time.

Estimating a person’s BAC involves a simple mathematical calculation based on several factors. If you know some of the factors, you can often calculate a range for the unknown factors.

Several companies have developed online BAC calculators that help attorneys double-check a BAC reading after a breath or blood test.

The BAC calculators can also help attorneys determine when they need to retain an attorney to explain an unexpected or unlikely result given the known variables in a particular case.

At best, an online BAC calculator based on all of the known inputs will only give a rough estimation of the BAC level. The more variables that are unknown, the less accurate the calculation.

Even when all of the main variables are know, the BAC calculation is still an approximation because no calculation can take into account all the factors and variations.

Factors Not Considered in BAC Calculators

Although BAC calculators provide a rough estimate, a variety of factors can make these estimates less accurate.

Factors that can affect the rate of abortion of alcohol in the body that are not considered or taken into account in these calculators include:

  • differing metabolism rates;
  • drinking frequency;
  • body fat percentage;
  • various health issues;
  • the combination of medications that might be taken;
  • hydration status;
  • fluid intake;
  • recent meals;
  • when food was eaten;
  • amount of food in the stomach and small intestine;
  • kidney function.

No blood alcohol calculator that is completely accurate because of the number of factors that come into play.

Those factors impact the consumption and reduction (burnoff) rates of different people under different circumstances.

What is BAC?

The term BAC refers to a Blood Alcohol Content which is the amount of alcohol in the bloodstream that is measured by grams of alcohol per 100 grams of blood.

BAC is measured as mass per volume. For example, if you have 8 grams of alcohol in 10,000 grams of blood, then the concentration of alcohol in the bloodstream is 0.08%.

As a general rule, Breath Alcohol Content (often referred to as the “BrAC”) is generally accepted to be proportional to the amount of alcohol present in the blood (BAC).

Under ideal testing conditions, a blood or blood test can be an effective way of determining BAC in some cases.

Although breath testing is considerably less accurate as blood testing, it is used in DUI enforcement because it is less intrusive, easier to administer, and far cheaper.

Charts for a BAC Level of Impairment

  • 0.00 – 0.03% Normal behavior with no impairment and normal behavior;
  • 0.03 – 0.06% Decreased inhibitions with mild euphoria and impairment;
  • 0.06 – 0.10% Buzzed, euphoric, increased impairment;
  • 0.10 – 0.20% Drunk, emotional swings, slurred speech, nausea, loss of reaction time and motor control;
  • 0.20 – 0.30% Confused, nauseated, poor mentation, blackout;
  • 0.30 – 0.40% Possibly unconscious, unarousable, loss of bladder function, risk of death;
  • Above 0.40% Impaired breathing, unconscious, coma, risk of death.

Common Factors Use by Online BAC Calculators

The most common factors used in an online calculator include:

  1. Age: Year
  2. Weight: Pounds
  3. Gender:  Male / Female
  4. Drinking time: Hours
  5. Glasses of water: 12 oz glasses
  6. Select the beverage
  7. When the drinking began
  8. When the drinking ends

Determining Ethanol Content

How do you compare the ethanol content in different kinds of alcoholic beverages?

Beer= 12 oz X .05 % = .60 fl oz
Whiskey = 1 1⁄2 oz X .40 % = .60 fl oz
Wine = 5 oz X .12 % = .60 fl oz


When Determining a Custom Percent of Alcohol

When determining a custom percent alcohol using one of the online BAC calculators, keep in mind the following:

  • the proof of alcohol is double the percent (e.g. 80 proof alcohol is 40%)
  • for a mixed drink, only count the number of shots you put in and not the drink’s total volume.
  • ounces of beverage consumed: 1 beer = 12 oz.
  • glass of wine = 5 oz. / 1 shot = 1.5 oz

When determining the percentage of alcohol in a beverage, the following guidelines apply:

  • 1 beer = 4-7%
  • 1 glass of wine = 11-13%
  • 1 shot = 40%

Chart Showing the Proof of Hard Alcohol by Brand

This chart shows the proof of hard alcohol by brand. The proof of hard alcohol can vary. To determine the exact proof of the drink served, look the bottle.

Regular Beer (by Brand / % Alcohol)

  • Budweiser   4.82%
  • Coors 5.03%
  • Corona 5.03%
  • Genesee 4.70%
  • Guinness 4.27%
  • Heineken Dark 5.17%
  • Michelob   4.99%
  • Miller High Life 4.80%
  • Miller Genuine Draft 5.02%
  • Molson 6.04%
  • Samuel Adams 4.88%

Light Beer (Brand % Alcohol)

  • Amstel Light 3.96%
  • Natural Light 4.12%
  • Bud  Light 3.88%
  • Coors Light  4.36%
  • Michelob Light 4.52%
  • Miller Lite 4.40%
  • Molson Light 2.41%

Wine (Brand % Alcohol)

  • Dry White 12.2%
  • Red/Rose 12.5%
  • Champagne 12.2%
  • Mad Dog 14%
  • Light Wine 7.4%
  • Dessert Wine 18.8%

Bourbon / Whiskey Proof

  • Bar Stock 86
  • Old Grand-Dad 90
  • Yukon Jack 100
  • Wild Turkey 101

Gin Proof

  • Bar Stock 80
  • Bombay 86
  • Tangueray 95

Rum Proof

  • Bar Stock 80
  • Captain Morgan’s 151 151

Tequila Proof

  • Bar stock 76-80

Vodka Proof

  • Bar stock 80

Others Proof

  • Kahlua 54
  • Peach Schnapps 40
  • Peppermint Schnapps 60
  • Rumple Mize 100
  • Ouzo 92
  • Triple Sec 78
  • Everclear 190

Other Common Questions about BAC

When determining the BAC at the time of driving, the following questions often arise:

  • How must do you have to drink to get drunk?
  • How many – beers or shots or glasses of wine does it take to get to .08?
  • How long does it take for blood alcohol level to go down?
  • How much is .08?
  • What is blood alcohol level?
  • What is lethal blood alcohol level?
  • What is the normal blood alcohol level?

A good blood alcohol calculator can chart the expected changes to the BAC level over time.

To do this, the calculation requires information about the time that has passed since the last drink.

AlcoDroid Alcohol Tracker – Apps on Google Play

Many companies have even developed several different blood alcohol calculator apps, including the AlcoDroid Alcohol Tracker – Apps on Google Play. AlcoDroid is an alcohol consumption tracker, drinks diary, and blood alcohol content calculator. These kinds of apps are not a good way to determine when you are sober, but they are entertaining.

The AlcoDroid plots your BAC development in a chart and indicates when you get below the legal limit or back to sobriety.

Additional Resource

DUI Pro Blood Alcohol Simulator – For an annual subscription of $99 a year, you can access DUI Pro, the most advanced blood alcohol simulator used for more than 20 years. No other analytical tool calculates a range of values under both criminal and civil standards. Find over one thousand predefined drink profiles. Define your custom drink profiles. Find modifiable distribution, absorption, and elimination constants. Use high-quality PDF files. The program is easy to use by experts.

This article was last updated on Monday, September 16, 2019.