This Blood Alcohol Content Calculator estimates your approximate BAC based on body weight, sex-based body-water factor, drink size, alcohol percentage, number of drinks, and time since your first drink. It uses a simplified Widmark-style estimate and U.S. standard drink definitions. In the United States, one standard drink contains about 0.6 fl oz or 14 grams of pure alcohol, according to the National Institute on Alcohol Abuse and Alcoholism.
How To Use the Calculator
- Select Imperial or Metric.
- Enter your body weight.
- Choose the sex factor used for the estimate.
- Select a drink type, or choose custom.
- Enter the number of drinks.
- Check or edit drink size and ABV.
- Enter the time since your first drink.
- Choose a comparison threshold, then calculate.
The drink presets are only starting points. If your beer is stronger, your wine pour is larger, or your cocktail contains more alcohol, edit the size and ABV fields.
How This BAC Calculator Works
The calculator estimates blood alcohol content from four main inputs:
- Your body weight, because alcohol is distributed through body water.
- Sex used for the BAC estimate, because the formula uses different body-water factors.
- Alcohol consumed, calculated from drink size, ABV, and number of drinks.
- Time since your first drink, because the body gradually eliminates alcohol.
The result is shown as an estimated BAC percentage, such as 0.045% or 0.080%. BAC is commonly measured as grams of alcohol per deciliter of blood. NHTSA explains that BAC measures the weight of alcohol in a certain volume of blood, expressed in grams per deciliter. NHTSA
BAC Formula Used
This tool uses a simplified Widmark-style formula:
BAC = (A × 5.14 / (W × r)) – (0.015 × H)
| Symbol | Meaning |
|---|---|
| A | Total pure alcohol consumed, in fluid ounces |
| W | Body weight, in pounds |
| r | Alcohol distribution ratio, using 0.73 for male estimate and 0.66 for female estimate |
| H | Hours since the first drink |
| 0.015 | Average BAC reduction per hour used by this calculator |
The formula is useful for an estimate, but it is not exact. Real BAC depends on how quickly alcohol is absorbed and eliminated by your body.
Italian sunset, a glass of wine and a car
U.S. Standard Drink Sizes
In the U.S., a standard drink contains about 0.6 fl oz or 14 grams of pure alcohol. The amount of pure alcohol depends on both drink size and ABV. The CDC gives the same standard drink definition and notes that alcohol content depends on percent alcohol by volume. CDC
| Drink | Typical Size | Typical ABV | Approx. Standard Drinks |
|---|---|---|---|
| Regular beer | 12 fl oz | 5% | 1.0 |
| Light beer | 12 fl oz | 4.2% | 0.84 |
| Strong beer / IPA | 16 fl oz | 7% | 1.87 |
| Wine | 5 fl oz | 12% | 1.0 |
| Liquor shot | 1.5 fl oz | 40% | 1.0 |
| Cocktail | 4 fl oz | 20% | 1.33 |
| Hard seltzer | 12 fl oz | 5% | 1.0 |
U.S. BAC Thresholds and Driving
This tool is built for a U.S. audience, but it does not provide legal advice. Most U.S. states use 0.08 g/dL as the BAC limit for most adult non-commercial drivers, while Utah uses 0.05 g/dL. CDC also notes that impairment starts at lower BAC levels. CDC
| Threshold | Common U.S. Context | Important Note |
|---|---|---|
| 0.08% | Common adult driving threshold in most U.S. states | Not a “safe to drive” line. Impairment can occur below this. |
| 0.05% | Utah adult driving threshold and lower-limit comparison | Useful for stricter-limit comparison. |
| 0.04% | Commercial driver comparison | Commercial rules can be stricter. |
| 0.02% | Zero-tolerance / underage comparison | Underage and special-status rules vary by state. |
NHTSA states that at 0.08 g/dL, crash risk increases exponentially, and it is illegal in all 50 states, D.C., and Puerto Rico to drive at 0.08 or higher, except Utah where the limit is 0.05. NHTSA
What BAC Levels May Mean
These ranges are general educational estimates. People can be impaired at lower BAC levels, and symptoms vary widely.
| Estimated BAC | General Meaning |
|---|---|
| 0.000% | No alcohol remaining based on the calculator inputs. This does not prove safe driving ability. |
| 0.001% to 0.029% | Low estimated BAC. Impairment may still occur. |
| 0.030% to 0.049% | Mild impairment possible. Judgment and attention may be affected. |
| 0.050% to 0.079% | Impairment likely. Driving risk increases. |
| 0.080% to 0.149% | High impairment range, often at or above the common U.S. DUI threshold. |
| 0.150% to 0.299% | Very high estimate. Serious impairment risk. |
| 0.300%+ | Potentially dangerous alcohol level. Seek urgent help if severe symptoms are present. |
Why Your Real BAC May Be Different
BAC calculators are estimates. Your actual BAC can be higher or lower because of:
- Food eaten before or during drinking
- How quickly you drank
- Drink size and pour accuracy
- ABV differences between brands
- Body composition and hydration
- Medication or health conditions
- Absorption timing
- Individual metabolism
Alcohol absorption is not instant. Your BAC may continue to rise after you stop drinking, especially if the drinks were recent.
Time to Zero BAC
The calculator estimates time from now to 0.000% using an average elimination rate of 0.015 BAC per hour. This is only a rough estimate. It assumes the BAC estimate is already declining, which may not be true if alcohol is still being absorbed.
Nothing reliably makes BAC drop faster except time. Coffee, cold showers, food, water, or sleep may change how you feel, but they do not instantly remove alcohol from the bloodstream.
Important Safety Note
This BAC calculator is not a breath test, blood test, legal test, or medical tool. Do not use the result to decide whether to drive, operate equipment, swim, bike, ride a scooter, or do anything risky.
If you have been drinking, the safest choice is not to drive. If someone has vomiting, confusion, slow or irregular breathing, pale or bluish skin, unconsciousness, or cannot be awakened, seek emergency medical help now.
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