How to use the tile calculator
- Enter the area: length × width of the floor or wall, or the square footage if you know it.
- Enter the tile size in inches and choose the grout joint.
- Set the waste under Adjust assumptions, and the square feet per box from the carton if you want a box count.
- Read the tiles, boxes and grout, and add prices for a total.
The tile formula
Area per tile = (tile length + joint) × (tile width + joint) ÷ 144
Tiles = area × (1 + waste) ÷ area per tile, rounded up
Boxes = area × (1 + waste) ÷ sq ft per box
Worked example
A 10 × 12 ft floor with 12 × 12 in tile and 1/8 in joints
- Area 120 sq ft; with 10% waste 132 sq ft.
- Each tile with joint covers 12.125 × 12.125 ÷ 144 = 1.021 sq ft.
- 132 ÷ 1.021 = 129.3, so 130 tiles.
- Grout for 3/8 in thick tile: about 8.9 lb with 10% extra, one 10 lb bag.
Tiles per 100 sq ft (1/8 in joint, no waste)
| Tile size | Tiles per 100 sq ft |
|---|---|
| 3 × 6 in (subway) | 752 |
| 6 × 6 in | 384 |
| 12 × 12 in | 98 |
| 12 × 24 in | 49 |
| 18 × 18 in | 44 |
| 24 × 24 in | 25 |
Waste by layout
- Straight lay, simple room: 10%.
- Diagonal or many corners: 15%.
- Herringbone or chevron: 15 to 20%.
- Large-format tile (24 in and up): 15% or more; breakage costs more per tile.
Common mistakes to avoid
- Using nominal tile size only. Include the joint, or you over-order slightly on small tile.
- Too little waste. Cuts at walls and fixtures add up.
- Mixed lots. Tile from different batches can differ in shade and size.
- No spares. Keep a few tiles for future repairs; the same tile may not be available later.
Frequently asked questions
How many tiles do I need?
Divide the area by the area of one tile including its grout joint, then add waste. A 10 × 12 ft floor (120 sq ft) with 12 × 12 in tiles and 1/8 in joints needs 120 × 1.10 ÷ 1.021 = 129.3, so 130 tiles.
How much extra tile should I buy?
10% for straight layouts in simple rooms, 15% for diagonal or herringbone patterns, lots of cuts or large tiles, and keep a few spares for future repairs.
How many boxes of tile do I need?
Divide the area including waste by the square feet per box printed on the carton, and round up. Enter the box coverage under Adjust assumptions.
How many 12 × 24 tiles in a square foot?
One 12 × 24 in tile is 2 sq ft, so 0.5 tiles per sq ft (slightly fewer with the joint). 100 sq ft takes about 50 tiles plus waste.
How do I measure a room for tile?
Measure the longest length and width and multiply. For L-shaped rooms, split into rectangles and add them, or use the square footage calculator and choose "I know the area".
Do I need to subtract cabinets and tubs?
Yes for floors under fixed cabinets or a tub. Tile only where it will show, plus a little under the toe-kick.