Tile Calculator

How to use this calculator

1. Measure the area to tile. For L-shaped rooms, measure as two rectangles and add the results.
2. Subtract fixed items (bath, kitchen island) in Advanced options.
3. Enter the tile size and grout joint — joints add up: a 1/8 in joint on 12 in tile reduces count by about 2%.
4. Choose your layout pattern; the waste factor updates automatically unless you type your own.
5. Enter tiles per box from the box label to get a box count.

Method & assumptions

Tiles = Area ÷ ((Tile length + joint) × (Tile width + joint))
Tiles to buy = Tiles × (1 + waste %), rounded up
Boxes = Tiles to buy ÷ tiles per box, rounded up

Joint

grout joint width

Waste %

cuts, breakage and spares; depends on layout

Assumptions & limits

• Tiles are rectangular and the area is roughly rectangular.
• Waste defaults are typical ranges from installers, not a standard.
• Mosaic sheets: enter the sheet size and use 0 joint.

Rounding: purchase quantities are always rounded up to whole bags, boxes, sheets or bundles. See our methodology.

Worked examples

In depth: tile planning notes

How layout and tile size affect waste

Waste in tiling comes from cuts at the edges. In a straight grid, each cut tile at the wall often leaves an offcut that can be used on the opposite side, so 10% is usually enough. In a diagonal layout almost every edge tile is cut at 45°, and offcuts are harder to reuse — 15% is the norm. Herringbone and chevron need even more because every row starts and ends with an angled cut.

Tile size matters too. Large-format tiles over about 24 in (600 mm) produce big offcuts that cannot always be reused and are more likely to crack when cut, so allow a little extra. Small mosaics on mesh sheets cut cleanly and waste less. Small rooms waste proportionally more because a greater share of tiles touch a wall.

Grout joints, boxes and spares

The calculator adds the grout joint to the tile size, because a 12 × 12 in tile with a ⅛ in joint actually occupies 12⅛ × 12⅛ in. With small tiles and wide joints the difference adds up to several percent. Boxes are rounded up to whole boxes, and we recommend keeping at least a few spare tiles from the same batch — shade and size can vary between production runs, and replacing a cracked tile years later is much easier with a spare in the garage.

Adhesive coverage depends on the trowel notch, the tile size and the substrate. As a rough guide, a 50 lb bag of thinset covers about 40–50 sq ft with a ¼ × ⅜ in notch, and a 20 kg bag of tile adhesive covers 4–5 m² at a 6–8 mm bed. Check the bag for your tile, and back-butter large-format tiles for full coverage.

Before buying, dry-lay a row across the room to find the best starting line; this often reduces thin slivers at the walls and saves tiles.

Tips & common mistakes

• Check that all boxes share the same batch/lot number — shade can vary between batches.
• Dry-lay a row before setting to plan cuts so you don't end with slivers at a wall.
• Keep a few spare tiles after the job; discontinued tiles are hard to match.

Sources

1. Tile Council of North America – TCNA Handbook — checked 2026-10; verify before launch
2. Daltile – installation resources — checked 2026-10; verify before launch
3. The Tile Association (UK) — checked 2026-10; verify before launch

Default values (bag yields, coverage rates, densities) are typical figures from manufacturer literature. Always check the label on the product you buy.

Cite or embed this calculator

DIYCalcLab. “Tile Calculator.” Oct 18, 2026. https://diycalclab.com/tile/tile-calculator/

An embeddable version for blogs and contractor sites is planned.