How the count is worked out
The calculator takes the floor area, divides it by the area of one tile plus its share of grout, and rounds up. It then adds your waste percentage and rounds up again, so you never end up one tile short.
If you enter how many tiles come in a box, it also gives the number of boxes to order. Tile is usually sold by the full box.
A worked example
A 4 m by 3 m room is 12 m². Using 300 mm × 300 mm tiles with 3 mm grout lines, each tile takes 303 × 303 mm of floor. 12 m² divided by that is 130.7, so you need 131 tiles for the bare area.
Adding 10% for cuts brings the total to 143.8, which rounds up to 144 tiles. With 11 tiles to a box, that is 14 boxes. In imperial, a 10 ft by 12 ft room of 12 in tiles needs 120, or 132 with 10% extra.
Choosing the layout
A straight grid wastes the least. Brick-bond, herringbone and diagonal layouts need more cuts. Larger tiles can look good in big rooms but waste more in small or awkward ones.
Plan the layout from the centre of the room so cut tiles at the edges are not too thin, and check how the pattern meets the doorway.
Notes
This is an estimate for a rectangular floor. For walls, enter the wall length and height as the room length and width. Always check measurements twice before ordering.
Questions people ask
How many tiles do I need?
Divide the floor area by the area each tile covers, including its grout line, then add an allowance for cuts and breakages. A 4 m × 3 m room with 300 mm tiles and 3 mm grout needs about 131 tiles, or 144 with 10% extra.
How much extra should I buy for waste?
Around 10% for a simple straight layout is a common allowance. Diagonal patterns, large tiles, small rooms and rooms with many corners need more, often 15% or more.
Do grout lines change the number of tiles?
Yes, slightly. Each tile takes up its own size plus one grout line, so wider gaps mean fewer tiles are needed. The effect is small for narrow joints and bigger for small tiles.
How do I measure the room?
Measure length and width at the widest points. For L-shaped rooms, split the area into rectangles, calculate each one, and add the totals. Subtract fixed items such as a bath panel if tiles will not go underneath.
Why buy spare tiles?
Tile batches can vary in colour, and an exact match may be hard to find later. Keeping a box or a few extra tiles makes future repairs easier.