A tile job needs three things sized correctly: the tiles themselves, the thinset that holds them, and the grout that fills the joints. Most people size the tiles and forget the other two, then make an extra trip to the store mid job. This guide covers all three.
Sizing the tiles
Work out the area to cover, then divide by the area of one tile. Add 10 percent for cuts and breakage on a straight layout, or 15 percent for diagonal and patterned layouts. A 12 by 12 inch tile covers exactly one square foot, which makes the maths easy.
Tiles per 100 square feet
| Tile size | Covers each | Tiles per 100 sq ft (+10%) |
|---|---|---|
| 12 x 12 in | 1.00 sq ft | 110 |
| 6 x 6 in | 0.25 sq ft | 440 |
| 18 x 18 in | 2.25 sq ft | 49 |
| 12 x 24 in | 2.00 sq ft | 55 |
Worked example
A 100 square foot floor with 12 by 12 tiles, straight layout: each tile covers one square foot, so 100 square feet with 10 percent waste is 110 tiles. With 6 by 6 tiles, each covers a quarter of a square foot, so you would need four times as many, about 440. Smaller tiles mean more cuts and more grout too.
Thinset
Thinset coverage depends on the trowel notch and the tile size. Larger tiles need a deeper notch and use more. The bag states coverage for each notch size, so match your trowel to your tile and read the bag rather than guessing. A large format tile can use two to three times the thinset of a small one per square foot.
Grout
Grout depends on the tile size and the joint width. Smaller tiles and wider joints use more grout per square foot, because there is more total joint length. A mosaic uses far more grout than a large format tile. Grout bags carry coverage charts by tile size and joint width, so use those for your specific combination.
Keep spares
Set aside a few tiles after the job. Matching a discontinued tile or a different production run later is rarely possible, and a cracked tile is far easier to replace with a stored spare from the same batch than with a hunt through clearance bins.