Tile Calculator
Find how many tiles and boxes you need for a floor, wall or backsplash, plus how much grout to buy.
How many tiles do I need?
Tiles = Area (ft²) ÷ (Tile length × Tile width ÷ 144) × (1 + waste)
A 10 × 10 ft floor is 100 ft². A 12 × 12 in tile covers exactly 1 ft², so you need 100 tiles plus 10% waste: 111 tiles, or 12 boxes of 10. With 1/8 in joints and 3/8 in thick tile, plan on about 8 lb of sanded grout.
The tile count ignores the grout joints, which slightly overstates the number of tiles. That small cushion is welcome, because cut pieces at the edges are rarely reusable.
How much waste to allow
| Layout | Waste allowance |
|---|---|
| Straight lay, simple rectangular room | 10% |
| Brick / offset pattern | 10–12% |
| Diagonal, herringbone or many corners | 15–20% |
| Large-format tile (24 in and up) | 15% |
Buy all tiles from the same lot (dye lot or shade number) and keep a spare box for future repairs: discontinued tile is hard to match.
How much grout do I need?
Grout volume = Joint length × Joint width × Tile thickness
Smaller tiles and wider joints use much more grout. The calculator multiplies the total joint length per square foot by the joint width and depth, and converts the volume to pounds at about 0.067 lb per cubic inch for cured sanded grout, plus 10% for mixing and cleanup. Use unsanded grout for joints narrower than 1/8 in.
Frequently asked questions
How many 12×12 tiles are in 100 square feet?
Exactly 100, since each covers 1 ft². Buy about 110–115 to allow for cuts and breakage.
How many square feet are in a box of tile?
It varies by tile size. A box of 12×12 tile usually holds 10–15 ft²; the coverage is printed on the box.
Should I buy extra tile?
Yes. Add 10% for straight layouts and 15% or more for diagonal patterns, and keep a few spares for repairs.
Last reviewed October 2026. Results are estimates; check important decisions with a qualified professional.