How much extra tile should I buy?

About 10% for a straight layout, 15% or more for diagonal, herringbone, or a room with lots of cuts and corners. Keep a few spares from the same lot for future repairs — shades drift between production runs.

Why enter tiles per box?

Tile is sold by the box, and the count per box depends on the tile size — a box of 12×12s holds far fewer than a box of mosaics. Using the figure off your carton makes the box count accurate.

Does this cover the floor and walls?

Enter whatever area you're tiling — add up floor, wall, and backsplash areas separately and total them. Subtract large openings if you want a tighter number, but the waste allowance usually absorbs them.

Tile Calculator

Enter the area you're tiling and the tile size, and this gives the number of tiles — and boxes — to buy, with a waste allowance for cuts.

Tiles

110tiles

Boxes: 11 boxes
Area: 100 sq ft

How these numbers are worked out

The formula

One tile covers (width × length) ÷ 144 square feet. Tiles = area × (1 + waste) ÷ that coverage, rounded up. Boxes = tiles ÷ tiles-per-box, rounded up — tile is sold by the box, and the count per box is on the carton.

Constants and sources

Tiles = area × (1 + waste) ÷ ((tile width × length) ÷ 144), rounded up; boxes = tiles ÷ per-box, rounded up. Geometry; tiles-per-box is product-specific (from the carton).

How it was checked

Last reviewed June 16, 2026. Before this calculator was published, its formula, constants and worked example were checked in a separate, AI-assisted review that redid the arithmetic and tested the factual claims; the site owner then approved it for publishing. No engineer or tradesperson reviews these pages. Where a figure depends on the product (a density, a coverage rate, a bag size), it is either an input you can change above or a fixed planning value stated on this page, so check it against your product's label or your supplier.

Spot a wrong number or an outdated figure? Send a correction.

Worked example

100 sq ft of 12 × 12-inch tile (1 sq ft each), 10 per box, 10% waste: 100 × 1.10 ÷ 1 = 110 tiles → ⌈110 ÷ 10⌉ = 11 boxes.

FAQs

How much extra tile should I buy?: About 10% for a straight layout, 15% or more for diagonal, herringbone, or a room with lots of cuts and corners. Keep a few spares from the same lot for future repairs — shades drift between production runs.
Why enter tiles per box?: Tile is sold by the box, and the count per box depends on the tile size — a box of 12×12s holds far fewer than a box of mosaics. Using the figure off your carton makes the box count accurate.
Does this cover the floor and walls?: Enter whatever area you're tiling — add up floor, wall, and backsplash areas separately and total them. Subtract large openings if you want a tighter number, but the waste allowance usually absorbs them.