Tile Calculator
Enter the size of the area, the size of one tile and the width of the grout joint to see how many tiles to buy and how many boxes that is. Choose imperial or metric units, add a waste allowance for cuts and breakage, and set how many tiles come in a box.
Last updated November 3, 2026
Gap between tiles
Extra for cuts and breakage
Printed on the box
Result
130 tiles in 13 boxes
118 tiles cover 120 sq ft (11.148 m²); 10 tiles per box cover 10 sq ft.
| Amount | Tiles | Sq ft | m² |
|---|---|---|---|
| Tiles needed | 118 | 118 | 10.963 |
| With waste (10%) | 130 | 130 | 12.077 |
| Bought in boxes | 130 | 130 | 12.077 |
| Spare tiles | 12 | 12 | 1.115 |
Area method: surface area divided by one tile plus its joint, rounded up. Layout, cuts and pattern can change the real count, so check with your supplier.
Show the work
Formula: tiles = ceil(area / ((tile length + joint) x (tile width + joint))); with waste = ceil(tiles x (1 + waste / 100)); boxes = ceil(tiles with waste / tiles per box)
- Area: 10 ft x 12 ft = 120 sq ft (11.148 m²).
- Tile cell: (12 + 0.125) x (12 + 0.125) in, each tile plus one 0.125 in joint.
- Tiles: area / cell, rounded up = 118.
- Waste: 118 x (1 + 10%) rounded up = 130 tiles.
- Boxes: 130 / 10 per box, rounded up = 13 (130 tiles, 12 spare).
Result: 130 tiles in 13 boxes
How the number of tiles is worked out
tiles = ceil( area ÷ ((tile length + joint) × (tile width + joint)) )
boxes = ceil( ceil(tiles × (1 + waste ÷ 100)) ÷ tiles per box )
Every tile sits in a small cell made of the tile plus one grout joint, in both directions. The area is divided by the cell size and rounded up. This is the area method: it treats the surface as one sheet and does not draw rows, so it does not know where cuts fall at the walls.
Take a floor that is 10 ft by 12 ft, which is 120 square feet, or 17,280 square inches. With 12 in tiles and a 1/8 in joint, each cell is 12.125 in by 12.125 in, or 147.015625 square inches. Dividing gives 17,280 ÷ 147.015625 = 117.54, which rounds up to 118 tiles. Without a joint the same floor needs exactly 120 tiles.
The waste allowance is applied next and rounded up again. At 10 percent, 118 × 1.10 = 129.8, so you buy 130 tiles. With 10 tiles per box, that is 13 boxes.
See how we calculate for the formulas, sources and review schedule behind every calculator.
Also useful alongside this calculator: Square Footage Calculator, Length Converter and Volume Calculator.
How much extra to buy
Tiles break and edges need cutting. A common rule of thumb is about 10 percent extra for a straight layout, and the calculator starts there. Diagonal and herringbone layouts create more cut pieces along the walls, so people often allow 15 to 20 percent for them. These are rough guides only.
On the 10 ft by 12 ft example, 15 percent waste gives 136 tiles and 20 percent gives 142, against 118 with none.
Grout joints and tile size
The joint is the gap filled with grout between tiles. It is entered in inches for imperial units and in millimeters for metric, and the default is 1/8 in, or 3 mm. A wider joint means each tile covers more floor: a 1/4 in joint brings the example down to 116 tiles from 118.
The effect grows as tiles get smaller. With 6 in tiles the same room needs 461 tiles before waste and 508 with 10 percent waste. With 24 in tiles it needs 30 and 33. The joint must be smaller than the tile.
Working in boxes
The box states how many tiles it holds, so enter that in the Tiles per box field. If the box holds 12 tiles rather than 10, the same 130 tiles need 11 boxes, which is 132 tiles and 14 spares.
Buying from the same lot
Color and size can differ slightly between production batches, so buy everything for the job at once and check that the boxes share a lot number. Keep the leftovers for future repairs.
If the room is not a simple rectangle, measure it first with the Square Footage Calculator, then enter the total area here.
How to use the Tile Calculator
- Choose imperial (feet, inches) or metric (meters, centimeters, millimeters).
- Enter the length and width of the area, then the length and width of one tile.
- Set the grout joint and a waste percentage, 10 percent by default.
- Enter the tiles per box from the packaging.
- Read the tiles and boxes to buy, then use Copy, Print or Share.
Worked example
A 10 ft by 12 ft floor is 120 square feet. With 12 in tiles and a 1/8 in joint it needs 17,280 ÷ 147.015625 = 117.54, so 118 tiles. Adding 10 percent waste gives 118 × 1.10 = 129.8, so 130 tiles, and boxes of 10 make 13 boxes with 12 spares.
| Floor size | Tiles needed | With waste | Boxes |
|---|---|---|---|
| 10 ft × 10 ft | 98 | 108 | 11 |
| 10 ft × 12 ft | 118 | 130 | 13 |
| 12 ft × 12 ft | 142 | 157 | 16 |
| 20 ft × 20 ft | 392 | 432 | 44 |
Frequently asked questions
How many 12 inch tiles do I need for 100 square feet?
A 10 ft by 10 ft floor needs 98 tiles with a 1/8 in joint, or 108 with 10 percent waste, which is 11 boxes of 10.
How much waste should I allow for tile?
About 10 percent is a common allowance for a straight layout, and diagonal or herringbone patterns often call for 15 to 20 percent. Treat both as rules of thumb and ask your installer.
Does the grout joint change how many tiles I need?
Yes, a wider joint means each tile covers more floor, so fewer tiles are needed. On a 10 ft by 12 ft floor with 12 in tiles, no joint needs 120 tiles and a 1/4 in joint needs 116.
Why does the result show boxes as well as tiles?
Tiles are sold in whole boxes, so the calculator rounds up to the next full box. The extra tiles left over are spares for future repairs.
Does this work for walls, patterns or irregular rooms?
It measures a rectangle by the area method, so for an irregular room add up the sections first and enter the total area. Confirm the quantity with your supplier before ordering.