How to calculate tiles needed
To determine how many tiles you need, divide your total area by the effective area of a single tile (including the grout joint), then add a waste factor for cuts and breakage.
Step 1: Measure your area
Measure the length and width of the space in feet and multiply them to get square footage. For irregular rooms, break the space into rectangles and add them together.
Step 2: Calculate the effective tile size
Each tile effectively covers slightly more space than its face dimensions because the grout joint takes up room. Add the joint width to both the tile width and height, then multiply to get the effective tile area in square inches. Divide by 144 to convert to square feet.
Step 3: Add a waste factor
No tile installation uses exactly the calculated number of tiles. Cuts, breakage, pattern matching, and future repairs all require extra material:
- 10% — Standard for straight-grid and running-bond layouts with a simple rectangular room.
- 15% — Recommended for diagonal, herringbone, and basketweave patterns, which create more cut waste at the borders.
- 20%+ — For complex rooms with many angles, natural stone with variation, or handmade tiles like zellige.
Step 4: Round up to whole boxes
Tile is sold by the box. Once you have the total tile count with waste, divide by the number of tiles per box and round up — you can't buy a partial box.
Tile size chart — common formats
These are the most common tile sizes used in residential and commercial installations:
- Mosaic: 1×1, 2×2 (usually sheet-mounted)
- Subway: 3×6, 4×12
- Standard square: 6×6, 8×8, 12×12
- Large format: 12×24, 18×18, 24×24
- Plank/wood-look: 6×36, 8×48