FitAndFillTile Calculator: How Many Tiles and Boxes
Work out how many tiles and boxes you need for a floor or wall from its size, the tile size, the grout joint and a waste allowance.
How the calculation works
area (sq ft) = length × width − area not tiled tiles per sq ft = 144 ÷ ((tile width + joint) × (tile length + joint)) tiles to buy = area × tiles per sq ft × (1 + extra), rounded up boxes = area × (1 + extra) ÷ square feet per box, rounded up The 144 converts square feet to square inches, so everything is in the same unit. Each tile is counted with one grout joint beside it.
Worked example
A 12 ft × 10 ft floor is 120 sq ft. With 12 in × 24 in tile and no grout joint you need 60 tiles (2 sq ft each). A 1/8 in joint makes each tile occupy a little more space, so 59.1 fit.
Adding 10 % for cuts and waste gives 65 tiles. If each box covers 16 sq ft, you need 132 ÷ 16 = 8.25 boxes, so 9 boxes.
Assumptions and limits
- The area is a rectangle; use "Area not tiled" for tubs, islands and anything you will not tile.
- Each tile takes up its own size plus one grout joint, so the count uses (tile width + joint) × (tile length + joint).
- The default extra is 10 %. Diagonal or herringbone layouts and rooms with many cuts usually need more; the tool offers 15 % and 20 %, but those are rules of thumb, so ask your tile supplier.
- Box coverage is the square feet printed on the carton. Tile can vary between production lots, so buy everything from the same lot when you can.
Frequently asked questions
How much extra tile should I buy?
Lowe's suggests an extra 10 % for trim and waste, and that is this tool's default. Diagonal or herringbone layouts, small rooms and rooms with many cuts usually need more; 15 % or 20 % are common rules of thumb, so ask your tile supplier for their recommendation.
Why does the grout joint matter?
Every tile takes up its own size plus the joint beside it. Ignoring the joint makes you buy a few tiles you do not need, and the difference grows with smaller tiles.
Should I count tiles or boxes?
Tile is sold in boxes, and each box prints how many square feet it covers. Enter that number to see how many whole boxes to buy. The count of loose tiles is useful for checking the plan.
Can I use it for walls?
Yes. Enter the wall's length and height, and use "Area not tiled" for windows, doors or fixtures.
Does it matter which box I buy?
Tile can vary slightly in color and size between production lots. Buy everything for the job at once and check that the boxes share the same lot number, and keep a few spare tiles for future repairs.
Sources
- Lowe's Tile Flooring Calculator: "It is suggested that you purchase an extra 10% for trim and waste."
- Unit definition: 1 square foot = 144 square inches
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