UK standard roll sizes and why "how many rolls" answers vary online

The UK standard roll is 53 cm wide by 10.05 m long, giving about 5.3 m² per roll before waste, but wide "European" rolls (70 cm or more) and American rolls (66-69 cm, often sold by the double or triple roll) use different maths entirely. Always check the width and length printed on the label of the specific roll you are buying rather than assuming the UK standard.

Match repeats: straight match vs drop match

A "straight match" pattern repeats horizontally across the wall, so wastage from the repeat is fairly small. A "drop match" (also called an offset or half-drop repeat) staggers the pattern between adjacent strips, which typically wastes noticeably more paper per strip than a straight match at the same repeat size. If your paper's label says "drop match", add one extra roll to the total this calculator gives you as a safety margin.