The king is drinking (after a painting by Jacob Jordaens, (1593 -1678))

Based on recent formulas to calculate the ppm of alcohol in the blood.

Since 1932, the so-called Widmark formula has been used to estimate the blood alcohol content (BAV Blood Alcohol Value). The alcohol content in the blood depends on the amount of alcohol consumed, the relative amount of water in the body (a constant that is different for men and women), the body mass, the rate of breakdown and the time.
Watson et al. (1980) further refined this formula in terms of the total amount of water in the body. Widmark used a constant r * weight. G. Watson et al. Introduced other constants.
This improved formula also takes into account that it takes an average of half an hour to start the breakdown of alcohol.
The formula was validated in 2001 by repeated tests with drinking alcohol, the graphs show that the predicted BAV values do not deviate far from the measured BAV values.
(see Appendix 2 in Absorption and breakdown of alcohol in the human body M.P.M. Mathijssen & drs. D.A.M. Twisk R-2001-19) (1)
During the first half hour after a drink, the ppm indicated will not change due to the half hour delay for the breakdown of alcohol.
For the calculation of the number of grams of alcohol is usually based on 8 g / cl. The app uses the more accurate value of 7.89 g / cl.
(see Appendix 1 in Dossier alcohol VAD, Flemish expertise center for Alcohol and other Drugs) (2)
The app can be used worldwide to calculate the ppm, but due to the color indication of the ppm and the color indication on the analogue meter, it is mainly focused on Belgian legislation where 0.5 per mil and 0.8 per mil are anchor points in the legal limits.
For private drivers the limit is 0.5 ppm. The police can immediately collect an amount that has been 179 euros since 1 May 2017 or reach an amicable settlement for the same amount. A driving ban of at least three hours is given. The police judge can pronounce a fine of up to 3,000 euros and deny the right to send.
Penalties become heavier from 0.8 ppm. In an amicable settlement, you pay up to 600 euros (depending on the exact blood alcohol level). The right to drive is denied for at least six hours and the driver's license can be withdrawn immediately, a police judge can also impose an alcohol lock.
Anyone who has more than 1.2 per mil of alcohol in their blood must inevitably go to court. The judge can pronounce fines of 1,600 to 16,000 euros. For repeated violations, the fines become even heavier, from 3,200 to 40,000 euros (3)
The calculator only gives an indication of the alcohol level in your blood. The actual values may vary slightly depending on your condition, whether you have eaten or not, ... Under no circumstances is it a binding result. The results also do not precede the results of an alcohol check conducted by the police. You cannot derive any rights from the calculation. Not to the police and not to the designer of this app.

1) https://www.swov.nl/sites/default/files/publicaties/verslag/r-2001-19.pdf
2) http://www.vad.be/assets/dossier-alcohol
3) https://www.druglijn.be/drugs-abc/alcohol/wetgeving

dr. Luk Stoops 2018