How we worked it out
Updated as you change the numbers.
- Area = length × width = 10 ft × 8 ft = 80 sq ft.
- Each tile with its grout joint covers (12 + 0.125) in × (24 + 0.125) in ÷ 144 = 2.0314 sq ft.
- Tiles = 80 sq ft ÷ 2.0314 sq ft = 39.4 tiles.
- With 10% extra: 39.4 × 1.1 = 43.3, rounded up to 44 tiles.
Method and assumptions
Each tile takes up its own size plus half a grout joint on every side, which is the same as one full joint added to its width and length. The calculator divides the area by that, adds the extra for cuts and breakage, and rounds up to whole tiles and boxes.
Square inches are converted to square feet by dividing by 144 (12 × 12).
Tips
- Buy all your tile from the same lot (printed on the box) so the color matches, and keep a few spares for future repairs.
- Large-format tile (any side 15 in or longer) usually needs a flatter floor and more careful setting; ask about leveling clips.
- For a shower or room with several walls, work out each wall and add them up with “I know the area”.
Questions
How much extra tile should I buy?
About 10% for a simple straight layout and 15 to 20% for diagonal or herringbone patterns, small rooms with many cuts, or tile that breaks easily. Keep the leftovers for repairs.
How many 12 × 24 tiles do I need for 100 sq ft?
A 12 × 24 in tile covers 2 sq ft, or slightly more with a 1/8 in joint. 100 sq ft needs 50 tiles before extra (49.2 with the joint), so about 55 with 10% extra.
Sources
- Tile Council of North America (TCNA): Installation guidance and joint widths
Method and figures checked on . Every worked answer on this page is covered by an automated test. Found a mistake? Tell us.