Tiles are just area divided by area, plus waste. Work out the floor or wall area, divide by the size of one tile, and add a cutting allowance. The same measurement then sets the adhesive and grout you need — so one area figure buys the whole job.
Step 1: count the tiles
Divide the area by one tile’s area, then add waste. A 13 × 10 ft floor (130 sq ft / 12 m²) in 24 × 12 in (600 × 300 mm) tiles — 1.94 sq ft each — needs 130 ÷ 1.94 ≈ 67 tiles; with 10% waste, order 74. Convert that to boxes using the tiles-per-box figure on the packaging.
Step 2: allow for waste
| Layout | Waste |
|---|---|
| Straight / grid, small rooms | 10% |
| Diagonal, herringbone, many recesses | 15% |
| Large-format tiles | 15% (one bad cut wastes a whole tile) |
Below 5% is gambling — a single box short can mean chasing a discontinued batch.
Tile Calculator
Enter the area and tile size for tiles, boxes, adhesive and grout — with a waste allowance.
Adhesive and grout
A 50 lb (20 kg) bag of adhesive typically covers 40–55 sq ft (4–5 m²) with a ¼ in (6 mm) notch trowel for floors — less with the bigger notches large-format tiles need, more for thin wall tiles. Grout depends on tile size and joint width: big tiles have far less joint per square foot. A 24 × 12 in floor at ⅛ in (3 mm) joints uses only about 0.04 lb/sq ft (0.2 kg/m²), while small mosaics can use ten times that.
Buy it all at once
From one batch. Tile shade and calibration vary between production runs, and a later top-up rarely matches. Check the batch numbers on the boxes at collection, and keep a few spares after the job for future repairs — far cheaper than re-tiling a patch that no longer matches.
Working in metric?
Identical method — area in m² divided by one tile’s area in m². A 600 × 300 mm tile is 0.18 m², so a 12 m² floor needs about 67 tiles before waste. The calculator does both systems — just flip the units switch.