September 15, 2026 · Building & Materials · 4 min read

Tile Math: How Many Tiles and Boxes Do You Really Need?

Nothing stalls a tiling job like running out of tiles halfway through a wall — especially when that specific batch has sold out. Buying too many wastes money and storage space. The fix is simple arithmetic you can do before you even visit the shop.

Step 1: Measure the area

For a rectangular room, multiply length × width. A 4 m × 3 m room is 12 m². For walls, measure each wall's height × width and add them together (you can subtract doors and windows, or leave them in as extra waste margin).

L-shaped or irregular room? Split it into rectangles, or trace the whole outline with the Irregular Surface Area Calculator and start from its total.

Step 2: Find the coverage of one tile

Tile size is usually printed in centimeters. Convert to square meters:

30 × 30 cm tile = 0.09 m²
60 × 60 cm tile = 0.36 m²
30 × 60 cm tile = 0.18 m²

Step 3: Divide, then add waste

Tiles needed = area ÷ tile coverage. For our 12 m² room with 60 × 60 cm tiles: 12 ÷ 0.36 = 33.3 → 34 whole tiles at minimum.

Now add the waste allowance — this covers cuts, breakages, and spares for future repairs:

10% for a simple straight lay in a rectangular room
15% for diagonal, herringbone or brick patterns, or rooms with many corners and alcoves

34 × 1.10 ≈ 38 tiles for a straight lay.

Step 4: Convert to boxes

Tiles are sold in boxes with a stated coverage — for example, "4 tiles per box, 1.44 m²." Divide your total area (including waste) by the box coverage and round up: 13.2 m² ÷ 1.44 = 9.2 → 10 boxes.

Tip: the Tile Calculator does all four steps at once — enter the room and tile dimensions, your waste percentage and the price per box, and it returns tile count, box count and total cost.

Practical tips from the trade

Buy all boxes from the same batch. Tile color varies slightly between production runs — check the shade code on the box.
Keep 2–3 tiles after the job. Future cracks and chip repairs are much easier with spares on hand.
Don't forget adhesive and grout. A 60 × 60 cm floor tile typically needs 4–6 kg of adhesive per m² depending on flatness.

Also working out materials for a build? See How Much Concrete Do You Need? for slabs, footings and mixing by the bag.

And if part of a wall stays painted rather than tiled, the Paint Calculator estimates the litres and cans for what's left.