BAC Calculator
Time Since First Drink
Amount of Alcohol Consumed
Standard & Custom| Type | Amount | Size | ABV (%) |
|---|---|---|---|
| 🍺 Beer | % | ||
| 🍷 Wine | % | ||
| 🥃 Liquor | % | ||
| 🍹 Other | % |
Safety & Intoxication
What Is BAC?
BAC stands for Blood Alcohol Concentration or Blood Alcohol Content. It estimates how much alcohol is present in the bloodstream and is commonly shown as a percentage, such as 0.08%.
Calculator Inputs
How the BAC Calculator Works
The calculator estimates BAC from body weight, biological sex, drink size, alcohol by volume, and time since the first drink.
- Body weight
- Body weight is used in the Widmark estimate because the same amount of alcohol generally produces a different BAC in smaller and larger bodies.
- Biological sex
- The calculator uses different alcohol distribution ratios for male and female inputs, which is common in BAC estimation formulas.
- Drink size and ABV
- A large drink, strong beer, or mixed drink can contain more alcohol than a standard serving, so size and alcohol by volume matter.
- Time since first drink
- BAC usually decreases over time as the body metabolizes alcohol. This calculator subtracts an estimated 0.015 BAC per hour.
Measurements
What Is a Standard Drink?
In the United States, one standard drink contains about 0.6 fluid ounces, or 14 grams, of pure alcohol. Serving sizes can vary, so one glass or cocktail may contain more than one standard drink.
| Drink type | Typical serving | Typical ABV | Pure alcohol |
|---|---|---|---|
| Beer | 12 fl oz | 5% ABV | About 0.6 fl oz pure alcohol |
| Wine | 5 fl oz | 12% ABV | About 0.6 fl oz pure alcohol |
| Liquor | 1.5 fl oz | 40% ABV | About 0.6 fl oz pure alcohol |
The Math
BAC Calculator Formula
A common BAC estimate uses the Widmark formula. It estimates alcohol concentration from alcohol amount, body weight, sex-based distribution ratio, and elapsed time.
Widmark formula
A is total pure alcohol in fluid ounces, W is body weight in pounds, r is alcohol distribution ratio, and H is hours since drinking began.
Pure alcohol
This step converts drink volume and alcohol strength into fluid ounces of pure alcohol.
- 1
Calculate pure alcohol
Pure Alcohol = Drink Size x ABV / 100. Example: 12 oz beer x 5% = 0.6 oz pure alcohol.
- 2
Calculate raw BAC
Apply the Widmark formula before subtracting the time adjustment. Example: (1.8 x 5.14) / (160 x 0.73) = 0.0792.
- 3
Subtract metabolism
The calculator subtracts about 0.015 BAC per hour. Example: BAC = 0.0792 - (0.015 x 2 hours) = 0.0492%.
BAC Levels
Common BAC Levels and Effects
Effects can vary by person, but impairment generally increases as BAC rises. Judgment, coordination, reaction time, and driving ability can be affected before a person feels severely intoxicated.
| BAC range | Possible effects |
|---|---|
| 0.01%-0.03% | Mild changes may begin |
| 0.04%-0.06% | Lowered inhibition, relaxation, slower reaction |
| 0.07%-0.09% | Judgment, coordination, and reaction time can be impaired |
| 0.10%-0.15% | Significant impairment, poor coordination, slower response |
| 0.16%+ | Serious impairment and increased health risk |
Safety
Important BAC Safety Note
A BAC Calculator should never be used to decide whether it is safe to drive, operate machinery, or do anything that requires focus, coordination, and quick reaction time.
Accuracy
Common Mistakes When Estimating BAC
BAC estimates become less useful when drink sizes, alcohol strength, or timing are entered incorrectly.
- Counting drinks incorrectly
- A large drink may contain more than one standard drink. A strong cocktail or large beer may contain much more alcohol than expected.
- Ignoring ABV
- Alcohol by volume matters. A 12 oz beer at 8% ABV contains more alcohol than a 12 oz beer at 5% ABV.
- Assuming coffee lowers BAC
- Coffee may make someone feel more awake, but it does not remove alcohol from the bloodstream.
- Thinking food removes alcohol
- Food can affect alcohol absorption, but it does not instantly lower BAC after alcohol is already in the bloodstream.
Frequently Asked Questions
A BAC Calculator estimates blood alcohol concentration based on body weight, sex, alcohol consumed, and time since drinking began.
BAC stands for Blood Alcohol Concentration or Blood Alcohol Content. It measures the amount of alcohol in the bloodstream.
A common formula is: BAC = (A x 5.14 / (W x r)) - (0.015 x H).
No calculator can guarantee exact BAC. It gives an estimate. Actual BAC depends on body composition, food, metabolism, medications, health, drinking speed, and other factors.
No. Never use a BAC Calculator to decide whether it is safe or legal to drive. Alcohol can impair driving even at lower BAC levels.
Many calculators use an average decrease of about 0.015 BAC per hour, but real metabolism can vary from person to person.
No. Coffee and water do not lower BAC. Time is the main factor that allows the body to metabolize alcohol.
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