Wallpaper measuring help!

[SmokeAndBone]

I am planning to wallpaper the chimney breast. I've chosen the paper and the design repeat is 53cm, 'half drop'. Rolls are 52cm x10m.

I know how to do the maths to work out how many rolls I need for the height and width of the breast, but I've no idea how to take account of the repeat in the design.

As the paper is £55/roll, I want to be as accurate as possible.

Please can someone help? My maths is terrible, I'm not proud of it.