Estimate your Blood Alcohol Concentration (BAC) using common U.S. inputs. This tool is for education only and is not a legal or medical test.
What this alcohol blood percentage calculator does
This calculator estimates your blood alcohol concentration (BAC), often called blood alcohol percentage, by combining body weight, biological sex, amount consumed, drink strength, and time. The estimate is based on the Widmark-style approach commonly used in educational tools.
BAC is usually expressed as a percentage. For example, a BAC of 0.08% means 0.08 grams of alcohol per 100 mL of blood. In many jurisdictions, 0.08% is a key legal threshold for driving under the influence, but legal limits vary and some places use lower limits.
How to use the calculator
- Enter your body weight in pounds.
- Select biological sex for distribution-ratio estimation.
- Enter the number of drinks consumed.
- Set average drink size and ABV (or use defaults like 12 oz at 5% for regular beer).
- Enter how many hours have passed since your first drink.
- Click Calculate BAC to see your estimated BAC and interpretation.
Quick drink examples
- Regular beer: ~12 oz at ~5% ABV
- Wine: ~5 oz at ~12% ABV
- Spirits (shot): ~1.5 oz at ~40% ABV
Understanding BAC ranges
The exact effects vary by person, but these ranges are often used for general education:
- 0.000–0.029%: subtle effects, possible mild relaxation.
- 0.030–0.059%: reduced inhibition, reduced alertness.
- 0.060–0.079%: noticeable impairment in judgment and reaction time.
- 0.080–0.149%: significant impairment; driving risk is high and often illegal.
- 0.150%+: severe impairment; risk of injury and alcohol poisoning increases.
How the estimate is calculated
The calculator uses this structure:
- Pure alcohol consumed (oz) = drinks × drink size (oz) × ABV fraction
- BAC estimate = (A × 5.14 / (weight × r)) − (0.015 × hours)
Where A is pure alcohol ounces and r is a sex-based body water constant (commonly 0.73 male, 0.66 female). The 0.015 factor represents average alcohol elimination per hour.
Important limitations
No BAC calculator can perfectly predict your real blood alcohol level. Results can be off due to:
- Food intake and stomach absorption timing
- Medication interactions
- Body composition and hydration status
- Metabolic differences and tolerance
- Pour-size errors and unknown true ABV
If you need an exact value for legal, employment, or medical purposes, only approved breath, blood, or lab testing should be used.
Safer planning tips
- Set a drink limit before you start.
- Alternate alcoholic drinks with water.
- Eat before and during drinking.
- Use rideshare, public transit, or a sober driver.
- If in doubt, do not drive.
Bottom line
This alcohol blood percentage calculator is a practical educational estimator to help you understand how intake and time can change BAC. Use it as a caution tool, not a green light. The safest BAC for driving and high-risk activities is always 0.00%.