How to use this blood alcohol calculator
This blood alcohol calculator estimates your blood alcohol concentration (BAC) using a common formula called the Widmark equation. To use it, enter your body weight, select your weight unit and biological sex, then enter how many standard drinks you have consumed. Finally, add the number of hours since your first drink and click Calculate BAC.
The result includes your estimated BAC, an impairment range, and an approximate minimum time to return to 0.000% BAC if you stop drinking now. It is meant for education and awareness—not as a guarantee of sobriety.
What this calculator is estimating
BAC is the amount of alcohol in your bloodstream, typically shown as a percentage. For example, a BAC of 0.080% means 0.08 grams of alcohol per 100 mL of blood. Many countries and states use BAC thresholds for DUI enforcement, but legal limits differ by location, driver type, and situation.
The equation used
The calculator uses a simplified Widmark model:
BAC = (A × 5.14 / (W × r)) − (0.015 × H)
- A = ounces of pure alcohol consumed
- W = body weight in pounds
- r = Widmark distribution ratio (typically 0.73 for men, 0.66 for women)
- H = hours since first drink
Each U.S. standard drink contains about 14 grams (roughly 0.6 fluid ounces) of pure alcohol.
Standard drink reference
Many beverages are stronger than people assume. A single can, glass, or pour may contain more than one standard drink.
| Beverage Type | Typical Serving | Approx. ABV | Standard Drinks |
|---|---|---|---|
| Regular Beer | 12 oz | 5% | 1.0 |
| Wine | 5 oz | 12% | 1.0 |
| Distilled Spirits | 1.5 oz | 40% | 1.0 |
| Strong IPA (16 oz at 8%) | 16 oz | 8% | ~2.1 |
How to interpret your BAC estimate
- 0.000–0.029%: subtle effects may appear.
- 0.030–0.059%: mild impairment in judgment, reaction speed, and coordination.
- 0.060–0.079%: clear performance decline, reduced attention and balance.
- 0.080–0.149%: significant impairment; often above legal driving limits.
- 0.150%+: severe impairment and high risk.
Even below legal limits, your driving ability can still be reduced. Impairment begins before most people feel “drunk.”
Why your true BAC may be different
No calculator can capture every biological and behavioral factor. Your actual BAC and impairment may vary due to:
- Drinking speed and drink strength variability
- Food in your stomach and hydration status
- Medication interactions
- Liver function and individual metabolism
- Body composition, age, and hormonal factors
- Measurement errors (pour size, ABV assumptions)
Frequently asked questions
Can coffee, cold showers, or exercise sober me up faster?
No. They may make you feel more alert, but they do not significantly speed up alcohol elimination. Time is the primary factor.
How fast does BAC go down?
A common planning estimate is around 0.015 BAC per hour, but real rates can be slower or faster. That uncertainty is one reason to avoid using estimates for driving decisions.
Is this calculator valid for legal defense?
No. Legal determinations rely on jurisdiction-specific standards and validated testing procedures. This tool is educational only.
Safer planning tips
- Set transportation plans before drinking (rideshare, taxi, sober driver).
- Track drink count and pace from the first drink.
- Alternate with water and eat regularly.
- Avoid mixing alcohol with sedating medications.
- If unsure, do not drive.
Bottom line
A blood alcohol calculator is useful for awareness, but it is not a real-time breathalyzer and not a guarantee of fitness to drive. Use estimates conservatively, prioritize safety, and choose a zero-risk transportation option whenever alcohol is involved.