Why Checkpoint Time Matters
If you drank the night before and need to drive the next morning, it's natural to wonder whether you'd still fail a checkpoint. This calculator uses the widely used Widmark formula to combine your drink type, quantity, body weight, and when you stopped drinking to estimate your current blood alcohol concentration (BAC) and when it's expected to drop below the common 0.03% legal driving limit.
How the Calculation Works
First, we estimate peak BAC by dividing total alcohol grams by body weight and a sex-based distribution ratio (0.68 for men, 0.55 for women). Then we apply the average elimination rate of about 0.015% per hour since you finished drinking to estimate your current BAC, and work backward to estimate when it will drop below the 0.03% threshold.
Legal Limits to Know
Many countries set the legal driving limit around 0.03% BAC, with harsher penalties like license suspension or criminal charges above 0.08%. Even a few drinks can keep you over the limit for several hours depending on your body weight and drink strength.
Important Notes
This calculator provides a Widmark-based reference estimate only. Actual elimination speed varies significantly with food intake, liver health, and individual metabolism. Even if the result shows you're under the limit, if there's any doubt, don't drive — use public transit or a designated driver instead.
Frequently Asked Questions
We estimate BAC using the Widmark formula, then assume it decreases by about 0.015% per hour, calculating when it drops below the 0.03% limit.
Many jurisdictions set it around 0.03-0.08% BAC; exceeding it can mean fines, license suspension, or criminal penalties.
Not necessarily. It's a reference estimate — actual BAC varies by metabolism. If in doubt at all, don't drive.