Estimate your blood alcohol content from sex, body weight, the number of standard drinks and how long ago you started, then see a sober-up timeline. A rough guide only – never use it to decide whether to drive.
Custom drink: set your own volume and strength
The line assumes your body clears alcohol at a steady rate of about 0.015% BAC per hour. The curve falls in a straight line until it reaches zero.
| Time from now | Estimated BAC | General effects |
|---|
Effect labels describe typical impairment in the general population. They are not legal categories and do not mean any level is safe.
For beginners: how to read this result
Real blood alcohol content depends on food, hydration, medication, health, tolerance, how fast you drank and many other factors this calculator cannot know. The number shown here can be far from your true BAC. Do not use it to decide whether it is safe or legal to drive, ride or operate machinery. There is no safe way to drive after drinking - if you have had any alcohol, do not drive.
Safety first. This calculator gives a rough, simplified estimate. It cannot tell you whether it is safe or legal to drive, ride or operate machinery, and your real blood alcohol content can be well above or below the figure shown. There is no safe way to drive after drinking – if you have had any alcohol, do not drive.
To get a result, load one of the example scenarios or enter your own values: pick your sex, choose kilograms or pounds and type your body weight, the number of standard drinks and the hours since your first drink. The advanced panel lets you replace the standard drink with a custom one defined by its volume and alcohol strength.
How blood alcohol content is estimated
The calculator uses the Widmark equation, the classic model behind most BAC tools. First it works out the total grams of pure alcohol consumed. One US standard drink contains about 14 g of alcohol; a custom drink is volume in millilitres multiplied by its alcohol by volume as a fraction and by 0.789, the density of alcohol.
That total is divided by your body water, approximated as body weight in grams multiplied by a distribution ratio – about 0.68 for men and 0.55 for women, reflecting average differences in body water. Multiplying by 100 gives the peak BAC as a percentage. Finally the model subtracts metabolism: the body clears alcohol at a steady rate of roughly 0.015% BAC per hour, so the longer it has been since your first drink, the lower the estimate. BAC is never allowed to fall below zero.
The sober-up timeline
Because alcohol leaves the body at a near-constant rate, the estimated BAC falls in a straight line. The chart and table plot that decline hour by hour until it reaches about 0.00%. The estimated time to zero is simply the current estimate divided by 0.015 per hour. Coffee, cold water, food or fresh air do not speed this up – only time lowers BAC.
Why the impairment labels are not legal advice
The result shows a general impairment category – minimal, mild, significantly impaired or severe – based on the estimated BAC. These describe typical effects across the population. They are not legal thresholds, they are not a measurement, and they never indicate that any amount of alcohol is safe before driving. Legal limits differ by country and region and are often well below the level at which a person feels impaired.
What this estimate does not include
The Widmark model assumes every drink has already been fully absorbed and ignores many real factors: food in the stomach, hydration, how quickly you drank, medication, illness, liver health, age, individual tolerance and exact body composition. Two people with identical inputs can have very different real BAC. Treat the number as a rough illustration of how alcohol and time interact, not as a personal safety reading.