Alcohol units
Grams of ethanol, 10 g drinks and UK units from volume and ABV.
Open a calculatorBreathalyzer
Log each drink with a time, a volume and an alcohol content, then choose a readout hour. Ethanol is added at the drink’s clock time and then falls at 0.15‰ per hour (Widmark: grams ÷ (kg × r); r = 0.68 for men, 0.55 for women). Absorption is treated as immediate — it is not. A drink after the readout hour is left out. Compare the estimate with a standard-driver limit. This is not a measurement. Do not use it to decide whether to drive.
kg
Drink log
Add what you drank and when. The chips only fill volume and %. The gauge is the estimate at the reading hour.
- ml%
- ml%
ml
%
Food, illness, the drink itself and how quickly you drank all change the real figure. A roadside breath test is an instrument. This page is only arithmetic.
Other countries
Standard drivers only. Tap a row to set the gauge.
RiverMath
Estimated BAC
0.00‰
0.000% BAC
Below 0.80‰ in England, Wales & Northern Ireland — still not a green light to drive
Ethanol logged28.8 g
Ethanol still in the body0.0 g
Time to 0.80‰0 min
Time to 0.00‰0 min
Standard-driver limits. Novices and professionals are often lower or zero. Elimination 0.15‰ per hour is an average. Sources: ETSC and IARD, 2026.
From the first drink
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An educational estimate. Not medical, tax or credit advice.