upd

Please refer to the Mapei grout calculator here Tile grouts calculator | Mapei

Design Tiles always recommends ordering an additional 10-15% on top of your order to allow for wastage. For larger format tiles like 600x1200mm, 750x1500mm, 900x1800mm or larger please allow for 20% extra waste.

Some rooms will require more cuts which generally means more wastage. Always confirm your quantities with your builder or tiler before proceeding with your order. Also, if you are purchasing tiles that are discontinued or on clearance its always worth buying extra as that tile, or batch of tiles may no longer be available from the manufacturer if you need to cover wastage.