How to calculate tiles
- Find the area: length × width. Split L-shaped rooms into rectangles and add them up.
- Find one tile’s area including the grout line.
- Divide the room area by the tile area and add waste.
- Divide by the number of tiles per box and round up.
Example: a 10 × 8 ft floor (80 sq ft) with 12 × 24 in tiles (2 sq ft each) needs 40 tiles, or 44 with 10% waste — 6 boxes of 8.
How much extra tile to buy
| Layout | Extra |
|---|---|
| Straight / grid layout, simple room | 10% |
| Offset or brick pattern | 10–15% |
| Diagonal or herringbone | 15–20% |
| Large-format tiles, many cuts | 15%+ |
Keep a few spare tiles after the job. Tile batches (dye lots) vary in color, and an exact match for a future repair can be impossible to find.
Common tile sizes
Popular floor tiles include 12 × 12, 12 × 24 and 24 × 24 inches (30 × 30, 30 × 60, 60 × 60 cm). Wood-look planks are often 6 × 24 or 8 × 48 inches. Backsplashes commonly use 3 × 6 inch subway tile or mosaic sheets — for sheets, enter the sheet size.
Grout gaps
Rectified porcelain often uses 1/16–1/8 in (1.5–3 mm) joints; handmade or rustic tile needs 1/4 in (6 mm) or more. Wider joints slightly reduce the number of tiles needed. Need the area of several rooms? Add them in the square footage calculator.
Frequently asked questions
How many tiles do I need for 100 square feet?
With 12×12 tiles, 100 tiles plus 10% waste — about 110 tiles.
How much extra tile should I buy?
10% for straight layouts and 15–20% for diagonal or herringbone patterns.
Does grout width change how many tiles I need?
Slightly — wider joints mean each tile covers a little more area.
How many 12×24 tiles are in a box?
Commonly 6–8 tiles, covering 12–16 sq ft. Check the box label.