Question: how many units of alcohol in 25 ml whisky?
Answer: A 1 litre (1,000ml) bottle of this whisky therefore contains 400ml of pure alcohol. This is 40 units (as 10ml of pure alcohol = one unit). So, in 100ml of the whisky, there would be 4 units. And hence, a 25ml single measure of whisky would contain 1 unit.