If the carpet tiles are 50cm x 50cm, you will need 4 carpet tiles to cover a square metre. If the tiles are 18” x 18” you will need to allow an extra 10%. If the tiles you have chosen are 480mm x 480mm you will need an extra 8% to allow for the adjustment. We recommend though, that you allow 10% extra for those awkward areas. For example, if you have a room that’s 5m [16’5”] x 4m [13’1”] that’s 20 sq metres. Add 10% allowance, and so you should order 22 square metres, which is 88 tiles. If you fancy going for a chequered pattern of 2 colours, then you’d simply order 44 of each. Click here to use our carpet tile calculator.