Estimate Your BAC
BAC estimates help you understand impairment and plan for safe transport. Actual BAC varies with metabolism, food, medications, and health status. Never rely on an online calculator to decide whether to drive.
Include time spent drinking.
Ethanol grams = Volume × ABV% × 0.789. Repeat for each drink to get total grams consumed.
Ethanol grams = Volume × ABV% × 0.789. Repeat for each drink to get total grams consumed.
Estimated BAC
0.03%
Legal driving limit in many regions: 0.05% or lower.
Total alcohol consumed
35.1 g
Equivalent to 2.51 US standard drinks (14 g each).
Impairment summary
Minimal effects, subtle mood elevation. Safe for most activities.
How to Use This Calculator
Track each drink
Enter volume and ABV% for every beverage consumed. Include mixed drinks by estimating total alcohol content.
Specify weight and sex
Widmark r factors differ by sex due to body water distribution. Weight conversions are handled automatically.
Adjust for time
BAC declines over time. Enter hours since first drink to account for metabolism (average 0.015% BAC/hour).
Formula
BAC (%) = [Total alcohol (g) ÷ (Body weight (g) × Widmark factor)] × 100 − (Metabolism rate × Hours)
Parameters:
- Total alcohol (g) = Σ (Volume (mL) × ABV% × 0.789)
- Body weight (g) = Weight (kg) × 1000 (or lb × 453.592)
- Widmark factor (r): 0.68 (male), 0.55 (female)
- Metabolism rate ≈ 0.015% BAC/hour (average)
Full Description
The Widmark equation estimates blood alcohol concentration based on alcohol absorbed, body water distribution, and metabolism. Individual factors such as liver function, medications, circadian rhythm, food intake, and genetics cause wide variability—this tool cannot guarantee legal or physiological safety. Use it for harm reduction education, plan alternative transportation, and recognise when hydration, food, or medical care is needed.
Frequently Asked Questions
How accurate is the calculator?
Estimates can be off by ±20% or more due to absorption variability. Do not rely on it to determine fitness to drive.
Does food intake matter?
Yes. Food slows absorption and can reduce peak BAC. This calculator assumes average absorption—results may differ.
What about medications?
Sedatives, opioids, some antidepressants, and sleep aids potentiate alcohol effects; extra caution is required.
When should I seek help?
Call emergency services if someone is unresponsive, vomiting repeatedly, has slow breathing, or shows signs of alcohol poisoning.