FitAndFillTile is sold by the box, but a floor is measured in square feet and every tile is a different size. Getting from one to the other takes four numbers: the area, the tile size, the grout joint and an allowance for cuts. This guide shows how they fit together.
Step by step
- Measure the area in square feet. If the room is not a plain rectangle, follow the guide to measuring square footage.
- Subtract what you will not tile, such as a tub, a kitchen island or a built-in.
- Find the real size of one tile and the width of the grout joint. Tile is often sold by a nominal size, so measure one tile or read the box.
- Work out how much floor one tile uses. It is the tile plus one joint on each dimension, not the tile alone.
- Divide the area by that, then add an allowance for cuts and breakage.
- Convert to boxes with the coverage printed on the carton, and round up.
The formula
tiles per sq ft = 144 ÷ ((tile width + joint) × (tile length + joint)) tiles to buy = area × tiles per sq ft × (1 + extra), rounded up The 144 is the number of square inches in a square foot, so the tile and joint sizes are in inches.
Worked example: a 12 × 10 ft floor with 12 × 12 in tile
The floor is 12 × 10 = 120 sq ft. With a ⅛ in joint, each tile uses 12.125 × 12.125 = 147.02 sq in, so 0.9795 tiles cover each square foot and the floor needs 117.5 tiles before any extra.
Lowe's tile calculator suggests buying an extra 10 % for trim and waste. With that, 132 sq ft of tile is 130 tiles. If the carton says it covers 15 sq ft, that is 132 ÷ 15 = 8.8, so 9 boxes.
A smaller room with something in the way
A bathroom floor 8 × 5 ft is 40 sq ft. If a 5 × 2.5 ft tub covers 12.5 sq ft, you tile 27.5 sq ft. In 12 × 24 in tiles with a ⅛ in joint, that is 13.5 tiles, or 15 tiles with 10 % extra.
How much the joint matters
The joint takes space, so a wider joint means fewer tiles for the same floor. For the 12 × 10 ft floor above, with 12 × 12 in tiles:
| Grout joint | Tiles per sq ft | Tiles to buy (10 % extra) |
|---|---|---|
| none | 1 | 132 |
| 0.0625 in | 0.9897 | 131 |
| 0.125 in | 0.9795 | 130 |
| 0.25 in | 0.9596 | 127 |
Ignoring the joint altogether would have you count 132 tiles instead of 130. The difference is small, but it is the kind of error that compounds on a large floor.
Common mistakes
- Using the nominal size. Measure one tile or read the box for the real size.
- Leaving out the extra. Cuts around walls and the occasional broken tile are certain; the extra is an allowance you choose. Diagonal layouts and rooms with many cuts usually need more, so ask your tile supplier.
- Forgetting that boxes are whole. Round up the number of boxes.
- Mixing production lots. Tile can vary between lots, so buy everything from the same lot when you can.
- Mixing square feet and square inches. Keep the tile and joint in inches and convert only with the 144.
Frequently asked questions
Do I need to count tiles for the grout joint on a wall too?
Yes, the formula is the same for a wall. Measure the wall area, subtract openings and use the same steps. The Tile Calculator works for floors and walls.
What if the tile has no box coverage on it?
Use the tile count. Divide the tiles you need by the number of tiles in a box to get the boxes, and round up.
Does this include grout and mortar?
No. This only counts tiles and boxes. Grout, mortar and spacers are sold with their own coverage; follow the label of each product.