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Areas

Floor tiling area (L-shaped room, less fixed units)

A=LW+LaWa−LoWo
where
A
net floor area to tile (m²)
L, W
main rectangle length and width (m)
La, Wa
extra rectangle length and width (m)
Lo, Wo
untiled area length and width (m)
Explain this equation

Gives the floor area to tile for a rectangular or L-shaped room, allowing for an area you will not tile under, such as kitchen base units or an island.

L × W is the main rectangle of the room. La × Wa is a second rectangle that sticks out of it, such as the short leg of an L or a bay. Lo × Wo is the footprint you are leaving untiled.

Any room made of rectangles can be added up piece by piece, as long as the pieces do not overlap. Taking away the untiled footprint leaves the area that actually gets tiles.

Sense check: a 4 × 3 m kitchen with a 1.5 × 1.2 m recess is 13.8 m²; deducting a 2.4 m run of 600 mm deep base units takes it to about 12.4 m².

Watch out: when splitting an L-shape, make sure the corner square is counted in only one of the rectangles.

Floor area for L-shaped or recessed rooms: one main rectangle plus one extra rectangle, less an area you will not tile under (kitchen units, island, fitted bath).

Enter your values to see the result.

Good to know

Split the room into rectangles that do not overlap. Decide whether you are tiling under units and appliances before deducting: many fitters tile under freestanding appliances and leave it under fixed base units. Doorway thresholds are small but worth adding where the tile runs through to a bar or trim.

Common mistake

Overlapping the two rectangles at the corner of an L-shaped room, which counts the overlap twice.

Limits

Rectangles only. Curved bays or splayed walls need approximating or measuring as triangles. No waste is added here.

Sources

Results are calculations from the published methods and manufacturer figures shown, and depend on the data you enter. Always follow the tile, adhesive and grout manufacturers’ instructions, BS 5385 and the Tile Association guidance. Coverage rates vary by product and substrate. Check prices and VAT rules with your own records and HMRC.