Full and double beds are the dimensions. 'Double' is the term used in the UK, whereas 'full' size is the name used in the US. Full-size dimensions are 53 x 75 inches, and double bed sizes are 135 x 190cm – which equate to almost the same size. Some retailers whose products are available in both the UK and the US may term their bed sheets as either double or full, so it's worth checking the exact dimensions to see which size you need.