Indicative alcohol calculator
A preventive estimate, starting from what you have consumed or plan to consume. It does not confirm that you can drive and does not replace medical or legal analysis.
What this calculator does and does not do
It is an educational, preventive tool for someone who has been drinking or plans to, and wants to assess the risk before getting behind the wheel. It is not a reconstruction tool for use after an event.
It does not start from a breathalyser reading, blood samples or a toxicology report, and it performs no retrograde calculation between two samples. Those belong to forensic expert evidence and case analysis, not to a calculator.
It never displays a conclusion that you are able to drive, never tells you how much you could drink to stay below a threshold, and never converts the result into a breathalyser value.
What the model is based on
Volumes of distribution, bioavailability, time to peak and elimination rates come from NHTSA, „Drugs and Human Performance Fact Sheets” 2024. Indicative strengths by drink type come from NIAAA and NHS material. The ethanol density of 0.789 g/ml is the figure used in the UK Government analysis of the Widmark formula.
The result is presented as a range of scenarios precisely because these are population ranges, not guaranteed biological limits for any individual.
If you have already been stopped
This calculator will not help. The discussion moves to procedure: the timing of sampling, chain of custody, the toxicology report and its interpretation. See the page on traffic offences.