What it works out
Count the tiles for a floor or a wall. Enter the area, the size of one tile and the grout joint. Each tile takes up its own size plus one joint, which is why a joint changes the count. Waste is added first, the total is rounded up once, and boxes follow from the tiles in a box. Waste starts at the usual figure for the trade; change it in the tool.
The formula
- Tiles
- area ÷ ((tile length + joint) × (tile width + joint))
- Order
- tiles × (1 + waste), rounded up
In words: Tiles = area divided by (tile length plus joint) times (tile width plus joint); order = tiles times one plus waste, rounded up
Worked example
A 100 ft² floor with 12 in by 12 in tiles and a 1/8 in grout joint
- Area 100 ft² = 14,400 in²
- Tile 12 in × 12 in
- Joint 0.125 in
- One tile with its joint = 12.125 × 12.125 = 147.016 in²
- Tiles = 14,400 ÷ 147.016 = 97.9
- With 10% waste: 107.7, rounded up to 108
Boxes follow from the number of tiles in a box.
Good to know
- Waste is your choice: diagonal layouts and cut-heavy rooms need more.
- Pattern repeats and tile thickness are not modelled.
- A calculator, not a building-code check: confirm local rules with your building authority.
Questions
Why does the joint change the count?
Each tile uses its own size plus one joint, so wider joints mean fewer tiles.
How much waste?
The tool starts at the usual figure for the trade. Raise it for diagonal layouts.