THE MATH, WITHOUT THE GUESSWORK
How to calculate how many tiles you need
Measure the surface you will tile, then enter its length and width. For an L-shaped room, measure each rectangular section separately and use + Add area to enter its length and width. The calculator adds the sections for you. Choose “I know my area” if you already have a total. For counter walls and windows, use the backsplash tile calculator to measure each wall section and subtract openings.
For individual tiles, use their actual face dimensions. For mosaic sheets, select Mosaic sheet and enter the actual coverage per sheet, plus sheets per box when buying full cartons. Individual tile dimensions still control the joint preview. Grout joints are not added to the tile face area, so the estimate leaves a little more material.
How Much Tile Do I Need for a Floor?
Measure a floor as rectangles and add them up. For an L-shaped room, draw a line across the inside corner and measure each rectangle separately. The same approach handles alcoves, closets and bay windows. Measure each wall at its widest point and round up to the next inch. Enter the first rectangle, then choose + Add area for each of the others. If your measurements include space you won’t tile, choose Subtract an area for it.
Subtract fixed cabinetry, not furniture. Tile usually stops at the face of base cabinets, so subtract the cabinet footprint. Do the same for a built-in island or peninsula, a tub and a built-in vanity. Don’t subtract anything you can lift or roll out, such as a refrigerator, range, dishwasher, washer, dryer or freestanding furniture. Tile goes under those, and buying that tile now is easier than matching a dye lot later.
Most floor cuts fall along the walls. That is why the default allowance depends only on the laying pattern: 10% for straight lay, 12% for half or third offset and 15% for diagonal or herringbone. Raise it for a room with many corners, doorways or fixed obstacles to cut around. Keep a spare box from the same batch for future repairs.
Worked Example: A 10 by 12 Foot Room
- Find the room area: 12 ft × 10 ft = 120 sq ft.
- Add your extra allowance: 120 × 1.10 = 132 sq ft.
- Divide by the tile area: a 12 × 24 inch tile covers 2 sq ft, so you need 132 ÷ 2 = 66 tiles.
How much extra tile to allow
Pattern changes the starting allowance, not the tile dimensions. These defaults estimate cutting and breakage; the calculator does not simulate a room layout.
| Pattern | Extra allowance | For a 120 sq ft room |
|---|---|---|
| Straight lay | 10% | 132.0 sq ft |
| Half or third offset | 12% | 134.4 sq ft |
| Diagonal | 15% | 138.0 sq ft |
If you adjust the percentage yourself, it stays at your setting when you switch patterns. Allow for any spare tiles you want to keep from the same batch.
Turn your estimate into boxes
Enter the square footage printed on the box for a coverage-based order. At 132 sq ft of required coverage and 16 sq ft per box, 132 ÷ 16 = 8.25, rounded up to 9 boxes. If the box only lists pieces, 66 tiles at 8 tiles per box rounds up to 9 boxes.
Use the optional Price per sq ft ($) input to estimate tile material cost from the rounded purchase. With 9 boxes covering 16 sq ft each at $4 per sq ft, tile purchase cost is 9 × 16 × $4 = $576. This counts tile only and excludes grout, mortar, labor and tax. The rounded box order may contain more tile than the requested allowance. Check that the tile size and box coverage match the product you are buying.