Tile Calculator
Before you buy tile, you need to know how many to get — and buying too few means a second trip (and a risk the batch has run out), while buying too many wastes money. This calculator works out the exact coverage, adds a wastage allowance for cuts and breakage, rounds up to whole tiles and, if you know the box size, works out how many boxes to buy and what they will cost. Enter the room and tile size in whichever unit you have to hand — feet and inches, or metres and centimetres — and mixing systems is fine, since everything is converted internally.
How to use the tile calculator
- Enter the room’s length and width, and choose feet or metres.
- Enter one tile’s length and width, and choose inches or centimetres.
- Set a wastage allowance — 10% is a common default, more for diagonal layouts or an inexperienced installer, less for a very simple straight layout with offcuts saved from a previous job.
- Optionally enter how many tiles come in a box and the price per box to get a shopping-list number and a cost estimate.
Formula
Tiles needed = (room area ÷ tile area) × (1 + wastage%), rounded up to a whole number, since you cannot buy part of a tile. If a box size is given, boxes = tiles needed ÷ tiles per box, also rounded up — which is why the actual tiles delivered (boxes × tiles per box) is usually a few more than the number you strictly need; those are your spares.
Worked examples
A standard bedroom
A 12 ft × 10 ft room tiled with 12 in × 12 in tiles and a 10% wastage allowance needs 132 tiles. That room is 120 ft² (11.15 m²), and each tile covers 0.092903 m². At 10 tiles per box costing $38 a box, that is 14 boxes ($532 total), delivering 140 tiles with 8 spare.
A bathroom in metric units
A 4 m × 3 m bathroom (12 m²) tiled with 20 cm × 20 cm tiles and 15% wastage needs 345 tiles. At 11 tiles per box and $22 a box, that is 32 boxes ($704 total), with 7 tiles spare.
Large-format tile
A small 6 ft × 8 ft room (48 ft², 4.459 m²) tiled with large 24 in × 24 in tiles needs only 13.2 tiles exactly before rounding, so 14 tiles with 10% wastage — large tiles need far fewer pieces than small ones for the same floor.
Planning a tiling project
Why tile size changes the count so much
Doubling a tile’s side length quadruples its area (a 24 in tile covers four times the area of a 12 in tile), so it takes roughly a quarter as many tiles to cover the same floor. Large-format tiles mean fewer joints to grout and often a faster install, but they can be harder to cut and to carry, and small rooms may show more visible trimming around the edges.
Common wastage allowances
| Layout | Typical allowance |
|---|---|
| Simple straight layout, rectangular room | 5–10% |
| Diagonal or herringbone layout | 15–20% |
| Room with many corners, alcoves or pipes | 15–20% |
| First-time DIY installer | Add a further 5% |
Buying in whole boxes
Because boxes cannot be split, the true "tiles received" number is always a round multiple of the box size at or above what you need. Keeping a few spares from the same batch is genuinely useful: tile ranges are frequently discontinued or shade-shifted between production runs, so a future repair may not match if you have to buy fresh stock later.
Measuring the room accurately
Measure the longest straight run in each direction rather than relying on a floor plan, since real rooms are rarely perfectly rectangular. For an L-shaped or irregular room, split it into rectangles, calculate each separately, then add the tile counts together (keeping one combined wastage allowance is usually close enough for planning purposes). For other area and volume calculations, see the geometry calculator.
Practice problems
Try these yourself first, then check your answer. The answers come from the calculator above.
- A 12 ft × 10 ft room is tiled with 12 in × 12 in tiles and a 10% wastage allowance. How many tiles are needed?
Show answer
Tiles to buy (rounded up, with wastage): 132
- A 4 m × 3 m bathroom is tiled with 20 cm × 20 cm tiles, 15% wastage, 11 tiles per box at $22 a box. How many boxes, and what is the cost?
Show answer
Tiles to buy (rounded up, with wastage): 345 · Boxes to buy: 32 · Estimated total cost: $704.00
Common mistakes to avoid
- Skipping the wastage allowance. Cuts around edges, doorways and pipes always use more tile than the flat area suggests, and offcuts are rarely reusable once a layout is set.
- Forgetting that box quantities round up twice: once for the tile count, and again when that count is divided into whole boxes — so the tiles you actually receive are usually a bit more than the raw calculation.
- Mixing units without noticing — entering the room in feet but the tile size in centimetres. Always check both unit dropdowns before reading the result.
- Using the exact tile count with no wastage at all; a shortfall discovered mid-job, from a since-sold-out batch, is far more costly than a few spare tiles.
Frequently asked questions
How many tiles do I need for a room?
Divide the room’s area by one tile’s area, then add a wastage allowance (commonly 10%) and round up to a whole tile, since partial tiles cannot be bought.
How much wastage allowance should I use?
Around 10% is typical for a simple straight layout. Diagonal layouts, intricate rooms with many corners, or a first-time installer often warrant 15–20%.
Why does it recommend more tiles than I need?
Because tiles are sold in whole boxes. Once your tile count is divided into boxes and rounded up, you usually receive a handful more tiles than the bare minimum — useful as spares for future repairs.
Can I mix feet and centimetres?
Yes — set the room unit and the tile unit independently; the calculator converts both to a common unit internally before dividing.
Reviewed September 26, 2026 by the SolveCalcPro editorial team. Found a mistake? Tell us; see our editorial policy.