Measure each room separately, add doorways, and deduct fitted cupboards and stairwells.
Measure length and width in each room and work out the areas separately. Combined measurements of irregular rooms almost always come out short.
Add doorways, alcoves and bays. Deduct fitted cupboards, chimney breasts and stairwells. The calculator on this site does the arithmetic for you.
Always order more than the net area. Square rooms laid straight manage on 5–8%, while angles, alcoves or diagonal laying need 10–15%.