Units are a clever way to help you know just how strong your drink is.
One unit of alcohol is 10 ml or 8g of pure alcohol. This equals one 25ml measure of whiskey.
Alcoholic drinks are made by fermenting and distilling natural starch and sugar.
Sprits can contain lots of calories. For instance, a 25ml measure 40% ABV shot of dark spirit, like whisky, with mixer contains 106 calories, similar to a chocolate mousse dessert.
Clear spirits contain slightly fewer calories than dark spirits but the calories in vodka and other clear spirits can still quickly add up.
A single 37.5% ABV vodka and tonic contains 96 calories, the equivalent of a crumpet.
Ordering a 50ml double spirit measure at a pub or bar makes your drink even more calorific - a double 37.5% ABV gin and mixer contains 149 calories, similar to a chocolate filled pancake.
Larger like any kind of alcohol, can stimulate the appetite and make calorific post-pub food like kebab and chips look more appealing.
How much is too much?
The government advises that people should not regularly drink more than the lower risk guidelines (14 units a week for men & women).