Tile Calculator
Calculate how many tiles you need for a floor, wall or backsplash. Enter the area, tile size and grout gap to get tile count, boxes and square footage with waste.
By CalcBuilt Editorial TeamUpdated September 9, 2026Formulas checked against manufacturer specs, see how we calculate.
Results
- Tiles to buy
- 44 tiles
- 40 tiles plus 10% waste; enter tiles per box to round up to full boxes
- Area to cover
- 80 sq ft
- Buy about 88 sq ft including waste
- Tile size
- 12 x 24 in
- 2 sq ft per tile. Side over 15 in: use leveling clips, an A118.15 mortar, a 1/2 in notch and a 33% offset at most
Tile formula
Area (sq in) = Length (ft) x Width (ft) x 144
Tile footprint (sq in) = (Tile width + grout gap) x (Tile length + grout gap)
Tiles = Area / Tile footprint x (1 + waste %), rounded upWorked example
A 5 x 8 ft bathroom floor with 12 x 12 in tile and a 1/8 in joint: 40 sq ft x 144 = 5,760 sq in. Each tile occupies 12.125 x 12.125 = 147 sq in. 5,760 / 147 = 39.2 tiles, plus 10% waste = 43.1, so buy 44 tiles.
Quick reference
| Tile size | Tiles per sq ft | Tiles per 100 sq ft |
|---|---|---|
| 3 x 6 in (subway) | 7.5 | 752 |
| 4 x 4 in | 8.5 | 846 |
| 6 x 6 in | 3.8 | 384 |
| 12 x 12 in | 0.98 | 98 |
| 12 x 24 in | 0.49 | 49 |
| 18 x 18 in | 0.44 | 44 |
| 24 x 24 in | 0.25 | 25 |
How to calculate tile
Convert the area to square inches, then divide by the footprint of one tile plus its grout joint. A 12 by 24 inch tile with a 1/8 inch joint occupies 12.125 by 24.125 inches, or 292.5 square inches. An 80 square foot floor (11,520 square inches) needs about 40 tiles before waste.
Add 10 percent for straight layouts and 15 percent for diagonal, herringbone or rooms with many cuts. Waste is cuts at the walls, culls in the box and breakage; buy full boxes from one dye lot and caliber and keep a box. Any tile with a side over 15 inches needs leveling clips, an A118.15 large-and-heavy-tile mortar, a 1/2 inch notch trowel and a floor flat to 1/8 inch in 10 feet.
Grout gap and layout
Joint width is set by the tile, not by taste. ANSI A108.02 calls for at least 3 times the tile's size variation and never under 1/16 inch. Any side over 15 inches in an offset pattern needs at least 1/8 inch. Rectified porcelain under 15 inches can run 1/16; ceramic runs 1/8 to 3/16; tumbled stone takes 1/4, polished marble and granite 1/16 to 1/8. Run 12x24 at a 33 percent offset at most; a 50 percent offset puts the bowed center of one tile against the ends of two and shows lippage.
What this calculator leaves out
The result is tile only. Thinset runs about one 50 lb bag per 50 to 60 square feet with a 1/2 inch notch under 12x24, plus grout, and cement board or an uncoupling membrane; tile never goes straight onto plywood. The floor must be flat to 1/8 inch in 10 feet and stiff to L/360 (L/720 for stone), with a movement joint every 20 to 25 feet indoors (TCNA EJ171). Special-order tile runs 2 to 6 weeks with 15 to 25 percent restocking on returns.
Mistakes that cost money
- 12x24 at a 50% offset with a 1/16 in joint shows lippage; ANSI A108.02 calls for 1/8 in minimum and a 33% offset at most.
- Ordering 44 tiles when the box holds 10 gets you 40 or 50; buy full boxes from one dye lot and caliber, and keep one.
- Standard thinset under 12x24 slumps and leaves hollow corners; use an A118.15 large-and-heavy-tile mortar with a 1/2 in notch.
- A subfloor out of flat by more than 1/8 in over 10 ft shows as lippage on large format; fix it with self-leveler first.
- Tile straight onto plywood cracks at the first seasonal swell; put down cement board or an uncoupling membrane over 3/4 in subfloor.
- Special-order tile takes 2 to 6 weeks and returns cost 15 to 25% restocking; confirm the count and the lot before the order goes in.
Key facts
- A 12 x 12 in tile covers 1 sq ft, a 12 x 24 in tile covers 2 sq ft, and an 18 x 18 in tile covers 2.25 sq ft.
- Add 10% waste for straight layouts and 15% for diagonal or herringbone patterns.
- Typical grout joints: 1/16 in for rectified porcelain under 15 in, 1/8 in minimum for any side over 15 in, 1/8 to 3/16 in for ceramic, 1/4 in for tumbled stone.
- Subway tile at 3 x 6 in takes 7.5 tiles per square foot with a 1/8 in joint, before waste.
Frequently asked questions
How many 12x12 tiles do I need for 100 square feet?
98 tiles with a 1/8 in joint, since each tile plus its joint covers just over a square foot. Buy 108 to 113 to allow for cuts and breakage, rounded up to full boxes from one dye lot.
How much extra tile should I buy?
10% for a simple straight layout, 15% for diagonal or patterned layouts. Round up to full boxes and keep a box for repairs; a later order will be a different dye lot and caliber.
What else do I need to buy besides the tile?
Thinset, about one 50 lb bag per 50 to 60 sq ft with a 1/2 in notch under 12x24, and an A118.15 mortar for anything over 15 in. Then grout, and cement board or an uncoupling membrane over the subfloor. Large format also needs leveling clips. None of that is in the tile count.
Sources and references
- Grout FAQ: standards for grout joint size and variation (Tile Council of North America)
- 2025 TCNA Handbook for Ceramic, Glass, and Stone Tile Installation (Tile Council of North America)
- TB89 Grout Coverage Rates: Understanding Variations (technical bulletin) (Custom Building Products)
Next steps for this project
The usual order for a flooring & tile project. See all flooring & tile calculators.
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Results are estimates based on standard formulas and typical product specifications. Confirm quantities with your supplier and local code before ordering.