I was not surprised to read in Lulie Halstead's article (OLN, Aug 10) that so many men and women were unable to give the correct answer to the question: "How many units in a large glass (25cl) of wine?" If asked, I would have to say: "I cannot give an answer until you tell me the alcoholic strength (abv) of the wine."
The higher the abv, the more units per glass. The abv must also be known to calculate the units per bottle (75cl).
It is my understanding that in the UK, a unit is 1cl (10ml) or 8gm of alcohol. Based on this, there is a fairly simple way to calculate the units per bottle (75cl) or units per 25cl glass:
1 litre (100cl) of a wine will contain, in units, the same number as the abv.
Thus a litre (100cl) of 12 per cent abv wine will contain 12 units.
Therefore, a bottle (75cl or ¾ of a litre) will contain ¾ of this, ie ¾x12 = nine units.
Since the 25cl glass is 1/3 of a bottle, this will contain 1/3x9 = three units of the 12 per cent abv wine.
Your readers may find this of help and, I suggest, will be surprised just how many units are contained in a glass (25cl) or bottle of high abv wine. Please do not let them go on thinking that it is only the glass or bottle size that decides the number of units.