Tile formula
Tile area = (Length + Grout) × (Width + Grout) ÷ 144
Tiles = Room area ÷ Tile area × (1 + Waste)
Tiles = Room area ÷ Tile area × (1 + Waste)
Example: A 10 × 8 ft floor (80 sq ft) with 12 × 12 in tiles and 1/8-inch grout needs 78.4 tiles. With 10% waste for a straight layout, buy 87 tiles — 9 boxes of 10.
Tips
- Measure irregular rooms as several rectangles and add them up.
- Buy all tiles from one lot and keep a few spares for repairs.
- Dry-lay a row to plan where cut tiles fall.
Outdoor pavers? Use the paver base calculator.
Frequently asked questions
How do I calculate the number of tiles?
Divide the area by the area of one tile including its grout joint, then add waste. An 80 sq ft floor with 12 × 12 in tiles and 1/8-inch joints needs about 79 tiles, or 87 with 10% waste.
How much extra tile should I buy?
10% for straight layouts, 15% for diagonal and 20% for herringbone or complex patterns. Add more for large-format tiles in small rooms.
Does grout width matter?
A little: a wider joint means each tile covers slightly more area, so you need slightly fewer tiles.
How many tiles are in a box?
It varies by size — check the box. 12 × 12 tiles often come 10–15 to a box; the calculator rounds up to whole boxes.