Blood Alcohol Calculator
Estimate blood alcohol content (BAC) using the Widmark formula
Estimated BAC
How to Use
- Select your gender (affects the distribution factor in the Widmark formula).
- Enter your body weight in kilograms.
- Enter the number of standard drinks consumed.
- Enter how many hours have passed since your first drink.
- Click 'Calculate BAC' and review the estimated result and disclaimer.
About Blood Alcohol Content
Widmark Formula
BAC is estimated using the Widmark formula: BAC = (drinks × 14 × 0.806) / (weight × r) − (0.017 × hours). Where r is the body water constant: 0.73 for males and 0.66 for females. 14 grams is the ethanol content of one standard US drink. BAC is expressed as grams per 100 ml of blood (percentage).
Legal Limits
Legal BAC limits for driving vary by country. Most countries set the limit at 0.05% (50 mg/100ml), including Australia, Germany, and most of Europe. The US, Canada, and UK set the limit at 0.08% (80 mg/100ml). Some countries have zero-tolerance policies. Professional drivers often have lower limits of 0.02%.
Effects by BAC Level
0.02–0.04%: Relaxation, mild mood elevation. 0.05–0.07%: Mild impairment of judgment and coordination. 0.08–0.10%: Significant impairment of driving ability (above legal limit in most countries). 0.10–0.15%: Slurred speech, loss of coordination. 0.15–0.30%: Severe impairment, possible blackout. Above 0.30%: Life-threatening risk.
Factors Affecting BAC
Food significantly slows alcohol absorption — a full stomach can reduce peak BAC by 30–50%. Body fat contains less water than muscle, concentrating alcohol in women (higher body fat %) compared to men. Medications can interact with alcohol and amplify effects. Individual genetic variation in alcohol metabolism (ADH enzyme activity) also affects BAC.
Key Features
- Uses the validated Widmark formula for BAC estimation
- Accounts for alcohol elimination over time
- Clear status categories with color-coded warnings
- Mandatory safety disclaimer for responsible use