How the tile calculator works
- Area = length × width, in square feet.
- Tile footprint = (tile width + grout) × (tile length + grout) ÷ 144. This is the area each tile covers including its share of grout line.
- Tiles = area ÷ tile footprint.
- Add waste and round up to whole tiles. If you enter tiles per box, the number of boxes is rounded up too.
Assumptions
- The tiled area is rectangular. For a backsplash, enter the wall length and backsplash height.
- Including the grout joint gives a slightly lower, more accurate tile count. For very small mosaics, sheets are usually sold by square foot instead.
- 10% waste covers cuts at edges and a few breakages. Diagonal layouts, large-format tiles and rooms with many corners can need 15–20%.
Worked example
A bathroom floor is 8 ft × 5 ft, using 12 × 12 in tiles with a 1/8 in grout joint and 10% waste.
- Area: 8 × 5 = 40 sq ft
- Tile footprint: 12.125 × 12.125 ÷ 144 = 1.021 sq ft
- Tiles: 40 ÷ 1.021 = 39.18, plus 10% = 43.1, which rounds up to 44 tiles
With 10 tiles per box, that's 5 boxes.
Tips before you buy
- Do a dry layout first. Starting from the center of the room gives even cuts at both walls.
- Buy tiles from the same lot or dye number. Shades vary between batches.
- Keep a few spare tiles after the job for future cracked-tile repairs.
Frequently asked questions
How many 12×12 tiles do I need for 100 square feet?
Without grout or waste, exactly 100. With a 1/8 in grout line and 10% waste, about 108 tiles.
How much extra tile should I buy?
Buy at least 10% extra for a straight lay. Use 15% for diagonal or herringbone patterns and 20% for large-format tiles in small or oddly shaped rooms.
Should I include the grout line in my calculation?
Including it is more accurate, especially with small tiles or wide joints, because the grout itself covers part of the area.