Tile Calculator

How This Calculator Works

The number of tiles needed for a floor is the room’s area divided by each tile’s effective footprint — its own size plus a share of the grout line around it — rounded up and padded with a waste allowance for cuts and breakage. Enter your room’s length and width, your tile’s size, the grout spacing between tiles, and a waste percentage, and this calculator returns exactly how many tiles to buy.

A wider grout line means each tile “claims” slightly more floor space than its bare dimensions, so fewer tiles are needed to cover the same room — the same reason large-format tile covers a floor with far fewer pieces than small mosaic tile.

The Formula

$$\vF{\text{Room Area}} = \vA{\text{Room Length}} \times \vB{\text{Room Width}}$$ $$\vG{\text{Effective Tile Footprint}} = (\vC{\text{Tile Length}} + \vD{\text{Grout Spacing}}) \times (\vE{\text{Tile Width}} + \vD{\text{Grout Spacing}})$$ $$\vH{\text{Tiles Needed}} = \frac{\vF{\text{Room Area}}}{\vG{\text{Effective Tile Footprint}}}\text{, rounded up}$$ $$\text{Recommended Order} = \vH{\text{Tiles Needed}} \times (1 + \text{waste percent} / 100)\text{, rounded up}$$

Tile projects conventionally budget more waste than a poured material like concrete or gravel, since cut pieces at room edges are often unusable scrap rather than reusable off-cuts — a 10% allowance is a common starting point, more for diagonal layouts or intricate room shapes.

Worked Example

A 4m x 3m room with 300mm x 300mm tiles, 3mm grout spacing, and a 10% waste allowance:

1. Room Area: $\vA{4} \times \vB{3} = \vF{12} \text{ sq m}$.
2. Effective Tile Footprint: $(\vC{300} + \vD{3})\text{mm} \times (\vE{300} + \vD{3})\text{mm} = 0.303\text{m} \times 0.303\text{m} \approx \vG{0.0918} \text{ sq m}$.
3. Tiles Needed: $\vF{12} \div \vG{0.0918} \approx 130.7$, rounded up to $\vH{131}$ tiles.
4. Recommended order (with 10% waste): $\vH{131} \times 1.10 \approx 144.1$, rounded up to 145 tiles.