This is a simple wallpaper calculator and should be used as a guide only. You can find the roll width and roll length you are after on the specific product page.
Roll widths are provided in meters (such as 0.5 x 10mtr) so your wall widths and heights should be inputted in meters also.
If you are purchasing an offset match product then you may need a little extra as there may be some waste. If you have any windows or doors in your walls you can simply ignore these. This will give a good estimate of required roll numbers.