Why Know Your Sobering Time?
Planning an early morning drive after a night out? Knowing roughly when your body will have processed the alcohol can help you make safer decisions. Alcohol is eliminated by the liver at a fairly constant rate — on average 0.015% BAC per hour — and no amount of coffee, cold showers, or energy drinks can speed that up. This calculator applies the Widmark formula to estimate your blood alcohol concentration (BAC) and the time until you reach zero.
The Widmark Formula Explained
The Widmark formula calculates BAC as: alcohol consumed (g) divided by (body weight (kg) × distribution factor r), multiplied by 100. Alcohol grams are derived from: volume (mL) × ABV (%) × 0.789 (density of ethanol). The distribution factor r is 0.68 for males and 0.55 for females, reflecting the difference in body water percentage between sexes. Sobering time is then BAC divided by the average elimination rate of 0.015% per hour.
Legal Limits Around the World
BAC limits for driving vary significantly by country. The United States sets a federal limit of 0.08%, as does the United Kingdom (England, Wales, and Northern Ireland). Scotland, most of continental Europe, and Australia use 0.05%. Some countries such as Japan (0.03%), Czech Republic and Hungary (0.00%) are even stricter. Always check the rules for the specific country or state where you plan to drive.
Important Limitations
The Widmark formula is a population-level average and cannot account for individual variation in liver enzyme activity, food intake, medications, or overall health. The actual time to sober up can differ significantly from the estimate. If you have any doubt about your sobriety, take a taxi, rideshare, or public transport instead of driving.
Frequently Asked Questions
A. The Widmark formula calculates BAC from alcohol consumed, body weight, and gender. Sobering time is BAC divided by the average elimination rate of 0.015% per hour.
A. It varies by country. The US and UK use 0.08%, most of Europe and Australia use 0.05%, and some countries use 0.03% or 0.00%. Check your local laws.
A. No. This is an estimate only. Individual metabolism varies. When in doubt, do not drive.