You can't calculate your alcohol limit.

The legal limit for driving is 80mg of alcohol per 100ml of blood. There is no fail-safe guide to how much you can drink to stay under this limit. The amount and type of alcholic drink, your height, weight and metabolism will all play their part.

It's a myth that you can calculate the amount of alcohol you are drinking. In fact, the alcohol content of beers, wines and spirits varies so greatly that to rely on guesswork like this is risking your licence and your life.

Several factors determine the level of alcohol in your blood:

1. Sex
2. Weight
3. Metabolism
4. Type and quantity of drink
5. Age

Any alcohol, even a small drink will impair driving ability.

The only safe course is not to drink and drive!

For your information, the following are all one unit of alcohol :-

a 1/2 pint of ordinary (3.5 per cent) strength beer or lager

a 25 ml pub measure of spirits (40 per cent)

a small (125 ml) glass of 9 per cent wine

a 50 ml pub measure of sherry, port or vermouth

SOME POPULAR DRINKS

A large (175 ml) glass of 12 per cent red wine - 2 UNITS

A bottle of 11 / 12 per cent wine - BETWEEN 8 AND 9 UNITS

A 330 ml bottle of 4 / 5 per cent lager or cider - 1.5 UNITS

A pint of 5 per cent export lager - 3 UNITS

A bottle of alcopops / ready mixed drinks - 1.5 UNITS

A can of strong (9 per cent) lager - 4 UNITS