It's not the MOST scientific but I've got the 'Morning after' app which tries to give you an idea when you can drive again after drinking.
I've input 3 standard glasses (175ml) of 15% wine and it says 9 hours
Always amazed the Police don't sit at the entrance to Sunday League grounds and breathalise there.
The percentage of people turning up at 9.30am after getting in at 3am must be huge.