How much extra tile should I buy for cuts and breakage?

Add 10–15% on top of the exact tile count for cuts, waste, and future repairs. The calculator includes 10% cutting waste by default.

Does grout width change how many tiles I need?

Yes. In this grid-layout approximation, each tile pitch includes one shared grout line in each direction, so wider grout lines mean fewer tiles fit across the same area.

Should I round up to whole boxes?

Yes. Tiles are sold in boxes, and you cannot buy part of a box. Round the tile count up to the next whole box so you never run short.

Are floor and wall tile sizes the same?

Floor tiles are often larger and thicker than wall tiles, but the calculation is identical — enter the actual tile dimensions from the box label.

How many bags of thinset do I need?

Divide the tile area plus a setting-material allowance by the coverage printed on the exact thinset bag, then round up. Coverage changes with trowel notch, tile format, back-buttering, substrate and product.

How much grout do I need?

Use the grout package's coverage for your tile dimensions, tile thickness and joint width. Divide the project area plus allowance by that coverage and round up to complete packages.

Tile, Grout & Thinset Calculator

Planning estimate only. Results are mathematical estimates based on the dimensions and assumptions you provide. Actual tile needs vary by layout pattern, room shape, and cuts. Always confirm the tile dimensions and tiles-per-box printed on your chosen tile packaging.

How this tile estimate works

The calculator first works out the area by multiplying length by width. It then approximates each tile pitch by including one shared grout line in each direction — (tile length + grout) × (tile width + grout) — and divides the area by that footprint. The result is multiplied by a cutting-waste allowance and rounded up to whole tiles, then rounded up again to full boxes.

How much thinset and grout do you need?

Thinset and grout are calculated separately from the tile count. Enter the square-foot coverage printed on the exact thinset bag and grout package, add an installation allowance, and the calculator rounds each result up to complete packages. This avoids a misleading universal bags-per-room assumption.

Thinset bags = ceil(area × allowance ÷ label coverage per bag)Grout packages = ceil(area × allowance ÷ label coverage per package)

Thinset coverage changes with the trowel notch, holding angle, substrate flatness, tile format, back-buttering and product formulation. Grout coverage changes with tile length, width and thickness, plus joint width and depth. When a manufacturer provides a coverage table or calculator for those dimensions, use its result as the coverage input here.

Common tile sizes

Tile	Imperial	Metric	Typical use
Mosaic / small	2 × 2 in	50 × 50 mm	Backsplashes, accents
Subway	3 × 6 in	75 × 150 mm	Kitchen and bath walls
Standard square	12 × 12 in	300 × 300 mm	Floors, walls
Large rectangle	12 × 24 in	300 × 600 mm	Floors, shower walls
Large format	24 × 24 in	600 × 600 mm	Large open floors
Large format	31.5 × 31.5 in	800 × 800 mm	Living rooms, open floors
Extra large	39.4 × 39.4 in	1000 × 1000 mm	Large open spaces
Porcelain slab	47.2 × 94.5 in	1200 × 2400 mm	Feature walls, shower walls

Large-slab planning: 1200 × 2400 mm slabs require specialist handling, cutting equipment, and a layout plan. Openings, corners, grain direction, and breakage can make a simple area-based 10% allowance insufficient; confirm whole-slab quantities with the installer or supplier.

Why grout width matters

Grout is not free space — it pushes every tile further apart. A tile that is 12 in wide with a 1/8 in grout line occupies 12.125 in of wall, not 12 in. Over a whole wall that difference adds up, which is why the calculator adds the grout width to the tile dimensions before dividing.

Real example: a 12 × 12 ft floor

A 144 sq ft floor tiled with 12 × 12 in tiles and 1/8 in grout lines has a base estimate of about 141.1 tiles, rounded up to 142 whole tiles. With 10% cutting waste the recommended quantity is 156 tiles. At 10 tiles per box that is 16 boxes — 160 tiles — including 14 tiles allowed for cutting waste plus 4 more from rounding up to full boxes.

Should you buy the exact calculated amount?

No — buy whole boxes and keep the spare. Tiles from different production runs can vary slightly in shade, so keeping extras from the same batch is essential for future repairs. A 10–15% waste allowance also covers cuts, breakage, and awkward corners.

What changes the estimate?

Layout pattern: Diagonal or herringbone layouts produce more waste than a straight grid.
Room shape: Non-rectangular rooms and many corners need more cuts.
Grout width: Wider grout lines reduce the number of tiles per area.
Tile size: Larger tiles cover more area per piece but lose more on partial cuts.
Box size: The tiles-per-box on the packaging controls the final purchase quantity.

Frequently asked questions

How do I calculate tile for a wall or floor?

Measure the length and width, multiply them for the area, then divide by the tile footprint including grout. Add a waste allowance and round up to whole boxes.

How many 12×12 tiles are in a box?

It varies by manufacturer, but 10 tiles per box is a common standard for 12 × 12 in tiles. Always read the packaging.

Do I need to leave room for grout in my measurement?

You do not measure grout separately — the calculator adds the grout width to each tile dimension automatically.

What if my room is not a perfect rectangle?

Break it into rectangles, calculate each separately, and add the results. For irregular shapes, add an extra allowance for cuts.

Before you buy

Confirm the tile dimensions and tiles-per-box on the actual packaging.
Add 10–15% waste for cuts, breakage, and future repairs.
Buy all tiles for one area at once to keep the shade batch consistent.
Store a few spare tiles for repairs later.

Installation-material sources

Coverage is intentionally editable because it is product- and installation-specific. For example, MAPEI's published grout coverage tables vary by tile size and joint width, while thinset manufacturers publish coverage by trowel notch and product. Confirm current figures using the selected product's package or technical sheet. See the MAPEI grout calculator as an example of dimension-specific grout coverage.

Editorial review

How this page was checked

Reviewed and maintained by Project Material Calculator. The review covers area and tile-pitch arithmetic, waste and box rounding, separate thinset and grout package calculations, unit conversion, and the worked example.

Formulas are covered by automated regression tests, and worked examples are checked independently against those formulas.
Product-dependent values remain editable. When manufacturer documentation is linked, it provides a traceable example; the current product label takes priority.
Tile layout, grout joints, cutting allowance, box rounding, thinset, and grout are checked as separate quantities.

Last reviewed: September 9, 2026. · Read the full methodology · Report a reproducible error

Tile Calculator: Tile, Grout & Thinset

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