Tile Wastage Calculator: How Many Tiles and Boxes to Buy
Find how many tiles to buy with a waste allowance for straight, diagonal or herringbone layouts: area, preset or custom tile size, grout joint, tiles per box, boxes to buy, leftover tiles and total cost.
How it works
tile coverage = (length + grout) × (width + grout) · base tiles = ⌈area ÷ coverage⌉ · tiles to buy = ⌈area ÷ coverage × (1 + waste %)⌉ · boxes = ⌈tiles ÷ tiles per box⌉
The number of whole tiles is the area divided by how much one tile covers, but that bare count assumes zero cuts and zero breakage, which never happens on a real floor or wall. The layout sets the waste: a straight grid typically needs about 10% extra for edge cuts, a 45° diagonal about 15% because every perimeter tile is cut on an angle, and a herringbone or similar pattern about 20% from the many short offcuts. Choose Custom waste % for something else, such as 5% in a large open rectangle or 25% in a small room with many jogs. Pick a preset size or enter your own length and width; under More options you can add the grout joint, which makes each tile cover slightly more area and trims the count. Tile is sold by the box, so enter the pieces per box to round up to whole boxes and see the spare tiles you will have left, and add a price per area, tile or box for the cost. Keep the spares sealed: a discontinued tile or a new production lot is hard to match years later.
Worked example
A 120 sq ft floor in 12 × 12 in tile (1 sq ft each) laid straight: 120 ÷ 1 = 120 field tiles. Adding 10% waste gives 120 × 1.10 = 132 tiles to buy; the extra 12 tiles cover perimeter cuts and the odd cracked piece. A diagonal layout would need 138 and herringbone 144. If the box holds 10 tiles you buy 14 boxes (140 tiles).
Sources: Inch Calculator: tile calculator and overage guidance · Calculator.net: tile calculator (grout gap, box and price inputs)
Frequently asked questions
How much waste should I add for tile?
About 10% for a straight or grid layout, 15% for a diagonal (45°) layout, and around 20% for herringbone and other patterns with lots of angled cuts. Large-format tiles and rooms with many jogs, niches and doorways push it higher, since each cut can leave an unusable offcut.
Should I calculate by tiles or by boxes?
Tile is sold by the box, so enter the pieces per box from the label and the calculator rounds up to whole boxes. Because you can only buy whole boxes you often end above the waste figure anyway; keep that surplus sealed for repairs.
Does the grout joint change how many tiles I need?
Slightly. Each tile plus its joint covers a bit more than the tile alone, so a 1/8 in (3 mm) joint on 12 in tile cuts the count by about 2%. The effect grows with narrow tiles and wide joints, such as mosaics and subway tile.
Why buy every tile at once?
Glaze color and size shift between production lots. Boxes from a single lot match; a reorder later can be visibly off, especially across a large open floor. Buying the full amount plus spares up front avoids a mismatched patch.
How do I measure the area to tile?
Multiply length by width for each rectangle and add them up; subtract fixed cabinets, tubs and islands. For walls use height × width and subtract windows and doors.
Related calculators
Estimate for planning. Confirm the pieces per box and coverage on your specific tile, and check the layout with your installer.