Before you punch numbers into any tile tool, decide two things on paper. First, are you laying the tile straight or on the diagonal? Second, how big is the tile? Those two choices set the waste factor, and the waste factor is where most orders either run short or pile up leftovers.
Map the tile to square feet
Each tile size covers a known area. A 12x12 tile is exactly 1 sq ft, so counting tiles for a rectangular room is almost mental math. An 18x18 tile covers 2.25 sq ft, which is why a box holds only four or five of them. A 12x24 tile covers 2 sq ft, so five tiles make a 10 sq ft box. A 24x24 tile covers 4 sq ft, and just three of them nearly fill a box.
Straight versus diagonal
A straight lay follows the walls, and most offcuts get reused. Ten percent waste covers cuts at the edges and a broken tile or two. A diagonal lay spins the grid 45 degrees, so every wall cut is angled and every corner eats a whole tile. That extra scrap pushes waste to 15%, and it also buys more bullnose trim along the edges.
Boxes, not pieces
Tile is sold by the box, not the piece. A typical carton holds about 10 sq ft. When the math says you need 132 sq ft with waste, you round up to whole boxes, never to half a carton. Open the boxes on site and shuffle tiles from different cartons so shade variation blends across the floor.
Order one box extra
Keep a sealed box after the job. Tile production runs shift shade by batch, and a chip next year will not match a fresh bag. The spare box costs little and saves a patchwork floor later.
Start the layout on the long wall
Snap a chalk line down the center of the room and dry-lay a row before you set anything. That center line tells you whether the cut tiles along the walls look even. If one wall would end in a sliver less than half a tile, shift the line over, because skinny cuts look bad and crack later. Grout comes separately, so budget a bag or two of matching grout on top of the box count.
Worked example
A 12 ft by 10 ft room with 12x12 tile, straight lay, 10% waste: about 132 tiles and 14 boxes. Switch to 12x24 on the diagonal and the same room lands near 69 pieces and 7 boxes.
Tile Calculator
A straight layout uses 10% waste, a diagonal layout bumps it to 15%, and every tile size from 12x12 to 24x24 maps to square feet per piece.
How to use
- Measure the room length and width in feet
- Pick the tile size, such as 12x24
- Choose a straight or diagonal layout
- Set the waste factor, 10% straight or 15% diagonal
- Read the tile count and boxes to order
Supported formats and limits
- Boxes usually carry about 10 sq ft of tile
- Diagonal layouts throw more cuts and need the higher waste
- Estimate only, rooms with jogs and niches use more
Examples
A 12 ft by 10 ft room with 12x12 tile and 10% waste lands near 132 tiles, about 14 boxes.Common errors
- Room length and width must be positive
- Waste should sit between 0 and 30 percent
Privacy and browser support
All calculations run locally in your browser. No room measurements are uploaded.
FAQ
How many square feet is each tile?
A 12x12 tile is 1 sq ft. An 18x18 tile is 2.25 sq ft. A 12x24 tile is 2 sq ft. A 24x24 tile is 4 sq ft.
Should I order 10 percent or 15 percent extra?
Ten percent is fine for a straight lay in a rectangle. Fifteen percent is the safe number for diagonal layouts, because angled cuts throw more offcuts.
How many tiles come in a box?
A typical box holds about 10 sq ft. For 12x12 that is 10 pieces; for 18x18 it is four or five; for 12x24 it is five. Always check the carton label.
Why does diagonal cost more?
Tiles cut at 45 degrees waste more of each piece, and the edges need more bullnose trim. The 15% buffer exists for exactly this.
How do I count a 12x24 layout?
Treat each tile as 2 sq ft. A 120 sq ft room needs 60 tiles before cuts, or about 69 with 15% diagonal waste.
Should I buy extra tile now?
Yes. Buy 10 to 15% up front and keep a box. Later batches from a new production run may not match the shade.