There are two ways of measuring the alcoholic strength
There are two ways of measuring the alcoholic strength of beer as a percentage: in percent by volume (or degrees) and percent by weight. Percent volume, or degrees, indicates the number of centilitres alcohol contained in 100 cl beer, whereas percent by weight gives the number of grammes alcohol in 100 g beer. Because alcohol weighs less than water, percentage by weight will always be lower than percentage of volume. Percent volume also happens to be the usual standard for other alcoholic beverages, such as wine and spirits. Beer of an alcoholic strength of 8.5% vol, or 8.5 degrees, contains 8.5 cl alcohol in 100 cl of beer. For one litre that would be 85 cl of pure alcohol. However, 85 cl alcohol is not the equivalent of 85 g beer per litre. Expressed as “g” it works out less, because of the lower specific gravity. Reckon on approximately 80 g alcohol per litre of beer 8.5% vol. That’s far too much to be healthy.