You'll need the right equipment to measure the width and height of your walls, and you can use a [tape measure](https://www.homebase.co.uk/tools/hand\\-tools/tape\\-measures.list) or a [laser measure](https://www.homebase.co.uk/bosch\\-zamo\\-laser\\-measure/12841303.html) for the most accurate results. Then you can figure out the area using a wallpaper calculator, but don't forget to consider space for windows and doors.