Start with the area you actually plan to tile, then allow for cutting and round the purchase to whole boxes. Keep measurements in one unit and record each room or wall separately. The Tile Calculator lets you add surfaces, subtract openings and compare box quantities.
Measure one surface at a time
For a rectangular floor, multiply length by width. A 4 m by 3 m floor covers 12 m². For a wall, multiply its width by the tiled height. Split an L-shaped room into rectangles that do not overlap. Measure any opening you will leave untiled and subtract its area from the relevant surface.
If two walls have the same dimensions and openings, use Copies rather than entering the same measurements twice. If they differ, add separate rows. In metre mode, openings are entered in square metres; in feet mode, use square feet.
Separate surface units from tile units
A room may be measured in metres while its tile dimensions are listed in millimetres. Choose the room unit and tile unit independently. A 300 mm square tile is 0.3 m by 0.3 m. The calculator includes the selected grout width in an approximate tile footprint; grout remains specified in millimetres.
Apply an allowance before rounding to boxes
For the 12 m² example, 300 mm square tiles and 3 mm joints give an approximate footprint of 0.303 × 0.303 = 0.091809 m² per tile. With a user-selected 10% extra allowance, the estimate is 144 tiles after rounding up. If a box contains 10 tiles, the order becomes 15 boxes, or 150 tiles.
The allowance is a planning choice. It is not a prediction of the exact waste for your layout. Diagonal patterns, narrow borders, damaged tiles and a requirement to retain matching spares can affect the amount you decide to order. Confirm the layout and stock requirements with the installer or supplier.
Check the order
- Confirm the same tile size and pack quantity used in the estimate.
- Review openings and repeated surfaces to avoid subtracting or counting them twice.
- Check whether the supplier sells individual tiles or whole boxes.
- Check batch and shade information when matching tiles across several spaces.
Use Area Calculator for component shapes and Paving Calculator for a separate paving estimate. A tile-area estimate does not determine adhesive, substrate preparation or an exact cutting plan.