The most usually used unit of measurement is the liter, although beer is traditionally served in pints (1 UK pint = 568 milliliters).

The standard commercial keg size in the UK is the 50-litre keg, which is widely used inpubs and restaurants. This size holds roughly 88 UK pints or around 105 U.S. pints of beer. It is ideal for establishments with high beer turnover and for serving popular draught brands.

Another regularly used size is the 30-litre keg, which provides about 52 UK pints. This smaller size is preferred by craft breweries, taprooms, and mobile bars, as it offers greater flexibility and permits a wider selection of beers to be served without committing to a full 50-litre volume.

Smaller kegs include the 20-litre keg (roughly 35 UK pints) and the 10-litre keg (roughly 17.5 UK pints), which are often used for limited-edition brews, small private events, or home bar systems. Even smaller are the 5-litre mini kegs, designed for personal use. These are popular for parties, barbecues, and home beer dispensers like PerfectDraft, and in general yield about 8.8 UK pints.

All UK beer kegs are ordinarily made from stainless steel or aluminum and are compatible with standardized coupler systems such as S-type or A-type. Choosing the right size depends on the type of beer being served, the venue's storage space, and the volume of expected consumption. Smaller kegs provide variety, while larger kegs are more cost-effective for high-demand settings.

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