How long after drinking can you drive safely?

To help avoid morning after drink driving, as a guide, you can work out the time it takes to sober up by counting units consumed, and, starting from one hour after finishing drinking, adding an hour for each unit.

This means that if you drink four pints of 4.5% larger, at 2.6 units each, and finish drinking at 11.00pm, you should avoid driving until at least 10.15am the next morning.

Three glasses of 250ml (that's a large pub measure) glasses of wine @ 14%ABV - if finished drinking at 11pm you're not be safe until 10.30am the next day.

The calculation is basically ABV x ml / 1000. You then start from an hour from when you finished drinking, adding an hour for each unit consumed.