Plan your tile without running short
Tile is sold by the box and shades vary between production lots, so it pays to buy the right amount up front. This calculator works out the area to tile, the number of tiles and boxes with the right waste factor for your layout, and estimates thinset and grout.
The formulas
- Area = length × width.
- Area to buy = area × (1 + waste %).
- Boxes = area to buy ÷ coverage per box, rounded up.
- Tiles = area to buy ÷ (tile length × tile width ÷ 144), with tile sizes in inches.
- Thinset: one 50-lb bag per about 90 sq ft for regular tile, about 50 sq ft for large-format tile.
- Grout: the manufacturers’ joint formula, (A + B) ÷ (A × B) × thickness × joint width × density, converted to pounds.
Worked example: a 12 × 10 ft floor in 12 × 24 in tile
Porcelain 3/8 in thick, 1/8 in grout joints, straight lay with cuts (10% waste), boxes of 16 sq ft at $4 per sq ft.
- Area: 12 × 10 = 120 sq ft.
- With waste: 120 × 1.10 = 132 sq ft.
- Boxes: 132 ÷ 16 = 8.25, so 9 boxes (144 sq ft).
- Tiles: each tile is 2 sq ft, so 132 ÷ 2 = 66 tiles.
- Cost: 144 × $4 = $576.
- Thinset: large-format tile, 120 ÷ 50 = 2.4, so 3 bags.
- Grout: about 6.4 lb, so one 10-lb bag of sanded or unsanded grout is plenty.
By layout
| Waste factor | Tiles | Boxes | Cost |
|---|---|---|---|
| 5% (simple straight lay) | 63 | 8 | $512 |
| 10% (straight lay with cuts) | 66 | 9 | $576 |
| 15% (offset or diagonal) | 69 | 9 | $576 |
| 20% (herringbone, patterns) | 72 | 9 | $576 |
Rounding up to whole boxes absorbs part of the waste on a small floor; on larger floors the difference between 5% and 20% is several boxes.
Installation points that affect quantities
- Large-format tile: tiles with any side 15 in or longer need a larger trowel notch and back-buttering for full coverage, which roughly doubles thinset use.
- Offset patterns: with long rectangular tiles, limit the offset to one third of the tile length to avoid lippage from tile bow.
- Substrate: the floor must be flat, typically within 1/8 in over 10 ft for tile under 15 in and 1/8 in over 10 ft with no more than 1/16 in over 2 ft for large-format tile. Self-leveling underlayment fixes low spots.
- Movement joints: leave a gap at walls and other fixed surfaces, hidden by baseboard, so the floor can expand.
Buying tips
Check that every box shows the same lot or batch number, and keep a few spare tiles for future repairs. For bathroom walls, subtract the tub or shower pan but add window returns, niches and shelves. If tiles are sold by the piece, divide the area to buy by the area of one tile and round up.