How to calculate how many tiles you need
Tile math is area divided by the size of one tile, plus waste for cuts around edges and any breakage. Because tile sizes are given in inches, each tile's area is converted to square feet before dividing.
area = length × width
tile sq ft = (tile L × tile W) ÷ 144
tiles = round up((area × (1 + waste)) ÷ tile sq ft)
Worked example
A 10 ft × 8 ft floor is 80 sq ft. A 12x12 tile covers 144 ÷ 144 = 1 sq ft. With 10% waste you need 88 sq ft of tile, so 88 tiles — which at 10 tiles per box rounds up to 9 boxes.
How much thinset and grout do you need?
Coverage depends heavily on tile size and trowel notch, but these are solid planning rules:
| Material | Coverage | Notes |
|---|
| Thinset (50 lb) | ~40–50 sq ft | Larger tiles use more |
| Grout (25 lb) | ~80–100 sq ft | Wider joints use more |
| Tile spacers | 1 per tile corner | Reusable |
Frequently asked questions
How many 12x12 tiles do I need for 80 square feet?
A 12x12 tile covers exactly 1 square foot, so 80 square feet needs 80 tiles, plus about 8 more for a 10% waste allowance — roughly 88 tiles.
How much extra tile should I buy?
Add 10% for a standard straight layout, 15% for diagonal, and 20% for herringbone or intricate patterns. Always keep one spare box for repairs.
How many bags of thinset do I need?
A 50-pound bag of thinset covers roughly 40 to 50 square feet with a standard trowel. Large-format tiles need more because of the thicker bed.
Should I seal grout?
Yes, most cement-based grout should be sealed after it cures to resist stains and moisture. Epoxy grout is an exception and does not need sealing.