How Accurate Are Online BAC Calculators?

Some drivers use online applications designed to estimate blood alcohol content (BAC), commonly known as ‘online breathalysers’ or ‘BAC calculators.’

A study aimed to evaluate the calculation methods of various ‘BAC calculators’ available online and assess their accuracy.

Researchers analysed the five most popular calculators found through Google, along with a commercial option. They tested these applications by inputting data from 10 alcohol consumption cases. The five applications required the following data: sex, height, weight, age, type and amount of alcohol consumed, stomach fullness, start and end times of alcohol consumption, and physique or alcohol metabolism rate.

They measured the actual BAC levels of these individuals using the Alcotest 7510 analyser and plotted alcohol metabolism curves. They then compared the real ethanol concentrations and the total time needed for complete alcohol elimination with the results provided by the applications.

The study revealed that the analysed ‘BAC calculators’ use different methodologies for their calculations. Both the peak alcohol concentrations and the time to reach these peaks varied across the applications. However, all calculators appeared to rely on the alcohol distribution coefficient established by Widmark.

The calculators also employed individual alcohol elimination rates ranging from 0.12 to 0.3‰ per hour. In most cases, the applications predicted that complete alcohol elimination would take longer than the actual observed time.

Online ‘BAC calculators’ can be useful for users in estimating the time needed for alcohol to be fully eliminated from the body, but their varying calculation methods can lead to different conclusions. Therefore, these tools should be used with caution, as they cannot replace reliable and evidentially acceptable breath tests.