Tile Calculator
Calculate how many tiles a floor or wall needs, including cuts and breakage, plus the cost.
How to use this calculator
- 1Measure the area. For an irregular space, split it into rectangles, work each out, and add them.
- 2Set the unit you measured in — the calculator converts everything for you.
- 3Check the coverage figure against the bag or tin you are actually buying; it varies between brands.
- 4Leave the waste allowance on. Running short mid-job costs far more than one spare unit.
How the calculation works
Units = ⌈ (Area × (1 + waste)) / Area of one piece ⌉- Area
- Surface area of the job
- waste
- Allowance for cuts, breakage and spillage
- ⌈ ⌉
- Round up — you cannot buy a fraction of a unit
Every dimension is converted to metres internally, so feet, yards and metres can be mixed with inches or centimetres without error.
Grout lines are ignored. They are typically 2–5 mm and slightly reduce the tile count, so leaving them out errs on the side of having enough.
Worked example
A 20 × 12 ft area
- 1.20 ft × 12 ft = 240 sq ft, which is 22.30 m².
- 2.Divided by the coverage per tile, that gives the raw requirement.
- 3.A 10% waste allowance is added, then the figure is rounded up to whole tiles.
Result: See the result panel — it updates live as you change the numbers.
What goes into a tiling job
Tiling is one of those jobs where the material itself — the tile — is only part of the estimate. Adhesive, grout, spacers, trim pieces, and often a backer board or membrane underneath all add to the total, and each has its own coverage rate that needs working out separately from the tile count.
The tile count itself comes down to area and layout: how much floor or wall needs covering, how big each tile is, and how much of what you buy will end up as an offcut rather than a whole piece in the finished job.
Common tile types
- Ceramic — the most common and generally least expensive option, suited to most floors and walls that aren’t exposed to heavy impact or extreme wear.
- Porcelain — denser and less porous than standard ceramic, which makes it more durable and better suited to high-traffic floors, exteriors, and wet areas.
- Natural stone — marble, travertine, slate and similar materials, prized for a look no manufactured tile fully replicates, but typically needs sealing and more careful maintenance.
- Mosaic — small tiles, usually pre-mounted on a mesh sheet, used for detail work, borders, and areas like showers where a lot of cuts and curves are unavoidable.
- Large-format tile — tiles significantly bigger than the old standard sizes, which means fewer grout lines and a cleaner look, but requires a flatter substrate and more careful handling to avoid cracking.
Planning the layout
The pattern a tile is laid in changes both how much waste to expect and how much skill the job needs.
- 1Measure the room and note obstacles — alcoves, cabinetry, and fixtures all reduce the usable area but often increase the number of cuts, which is the opposite of what a simple area calculation would suggest.
- 2Choose a layout — a straight grid is the most material-efficient; diagonal, herringbone and other patterns look striking but turn far more edge tiles into cuts.
- 3Dry-lay a row before committing — laying tiles out unglued along the main sightline shows how the cuts fall at the walls, so the pattern can be shifted before anything is fixed down permanently.
- 4Order everything in one batch — tile is produced in dye lots, and colour can shift noticeably between batches — buying enough for the whole job up front, including spares, avoids a mismatch later.
Where estimates commonly go wrong
- Underestimating waste on complex layouts — a straightforward rectangular room might only need 10% extra, but a diagonal pattern, a small bathroom with lots of cuts around fixtures, or a first-time DIY attempt can easily use 20% or more.
- Not buying spares — a few extra tiles set aside after the job means a cracked tile years later can be replaced from the same dye lot, rather than searching for a discontinued match.
- Forgetting grout and adhesive coverage — these are sold with their own coverage rates based on tile size and trowel notch size, and running short partway through a wall or floor is a bigger problem than running short on tile.
What this assumes, and where it stops
Assumptions
- The area is flat and regular as described. Slopes, steps and obstructions change the quantity.
- Coverage figures are the manufacturer’s stated values, which assume good conditions and an even surface.
- Tiles are laid in a straight grid unless you raise the waste allowance for a diagonal pattern.
Limitations
- This estimates material only — not labour, tools, delivery, hire or disposal.
- Manufacturer coverage varies between brands and batches. Always check the packaging.
- Does not calculate adhesive, grout or trim.
- Complex rooms with many cuts and alcoves need a higher allowance than the default.
Common questions
How much extra tile should I buy?
Ten per cent for a straightforward rectangular room, and 15–20% for diagonal or herringbone layouts where every edge tile is a cut. Buy it all in one order — tile batches vary in shade, and matching later is often impossible.
Should I include grout lines?
No — leaving them out is the safer error. A 3 mm grout line means slightly fewer tiles than the raw calculation, so ignoring it builds in a small extra margin on top of your waste allowance.
Formula and content last reviewed on .
Results are estimates for information only, not professional advice.
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