🧱 Tile Calculator
By ToolNimba Editorial Team · Updated 2026-06-19
Tiles are rounded up to whole units after the waste allowance, since you cannot buy part of a tile. The waste percentage covers cuts, breakages and a few spares for future repairs.
This tile calculator tells you how many tiles to buy for a floor or wall. Enter the room as a length and width (or type the area directly), enter the size of one tile, and set a waste percentage for cuts and breakages. You will instantly see the bare tile count, the count with waste added, the area to cover, and, if you enter tiles per box, how many boxes to order.
What is the Tile Calculator?
Working out a tile order is a simple area problem with one catch: you can only buy whole tiles, and some get cut or broken, so you always need a few more than the bare maths suggests. The method is to find the area you are covering, divide by the area of a single tile to get the raw tile count, add a waste allowance, and round up. This calculator does each step and shows the numbers so you can check them.
The units have to line up before you divide. A floor is usually measured in metres or feet, while a tile is sized in centimetres or inches, so a 30 cm tile is really 0.30 m on each side and covers 0.09 sq m, not 30 of anything. This tool converts tile dimensions into the same unit as the room automatically (dividing centimetres by 100, or inches by 12), which is the single most common place a hand calculation goes wrong.
The waste allowance matters more than people expect. A straight layout in a simple rectangular room wastes little, so 10% is a sensible default. Diagonal or herringbone patterns produce many more part-tiles, so 15% to 20% is wiser. Large-format tiles, an irregular room with lots of corners, or a first-time DIY job all push the figure up too. It is also smart to keep a few spare tiles from the same batch, because dye lots vary and an exact-match replacement years later is hard to find.
When to use it
- Estimating how many floor tiles to buy for a kitchen, bathroom, or living room before a trip to the store.
- Costing a wall-tiling job for a backsplash or shower by turning area and tile size into a tile and box count.
- Comparing tile sizes (for example 30 cm vs 60 cm tiles) to see how the count and likely waste change.
- Checking a contractor’s quote so you know roughly how many boxes the job should need.
How to use the Tile Calculator
- Pick metric (metres and centimetres) or imperial (feet and inches).
- Enter the room length and width, or switch to "By area" and type the area directly.
- Enter the length and width of a single tile in the small unit (cm or in).
- Set the waste percentage (10% is a good default; use 15% to 20% for diagonal or patterned layouts).
- Optionally enter the tiles per box, shown on the packaging, to get a box count.
- Read off the tiles to buy and the number of boxes.
Formula & method
Worked examples
A 12 ft by 10 ft floor with 12 in by 12 in tiles, 10% waste, 10 tiles per box.
- Floor area = 12 × 10 = 120 sq ft
- Tile size in feet = 12 ÷ 12 = 1 ft, so each tile covers 1 × 1 = 1 sq ft
- Bare tiles = 120 ÷ 1 = 120
- With 10% waste = 120 × 1.10 = 132 tiles
- Boxes = ceil(132 ÷ 10) = 14 boxes
Result: Buy 132 tiles (14 boxes of 10).
A 4 m by 5 m floor with 30 cm by 30 cm tiles and 10% waste.
- Floor area = 4 × 5 = 20 sq m
- Tile size in metres = 30 ÷ 100 = 0.30 m, so each tile covers 0.30 × 0.30 = 0.09 sq m
- Exact tiles = 20 ÷ 0.09 = 222.22
- With 10% waste = 222.22 × 1.10 = 244.44, rounded up to 245 tiles
Result: Buy 245 tiles.
A 200 sq ft area with 18 in by 18 in tiles and 15% waste for a diagonal layout.
- Area = 200 sq ft (entered directly)
- Tile size in feet = 18 ÷ 12 = 1.5 ft, so each tile covers 1.5 × 1.5 = 2.25 sq ft
- Exact tiles = 200 ÷ 2.25 = 88.89
- With 15% waste = 88.89 × 1.15 = 102.22, rounded up to 103 tiles
Result: Buy 103 tiles.
Suggested waste allowance by layout and situation
| Situation | Suggested waste |
|---|---|
| Straight (grid) layout, simple rectangular room | 10% |
| Diagonal layout | 15% |
| Herringbone or other complex pattern | 15% to 20% |
| Large-format tiles or many cuts and corners | 15% to 20% |
| First-time DIY installer | add about 5% on top |
Approximate floor tiles needed per 100 sq ft by tile size (straight layout, before waste)
| Tile size | Tile area | Tiles per 100 sq ft |
|---|---|---|
| 12 in × 12 in | 1.00 sq ft | 100 |
| 16 in × 16 in | 1.78 sq ft | 57 |
| 18 in × 18 in | 2.25 sq ft | 45 |
| 24 in × 24 in | 4.00 sq ft | 25 |
| 12 in × 24 in | 2.00 sq ft | 50 |
Common mistakes to avoid
- Mixing room and tile units. A floor measured in metres and a tile measured in centimetres are not the same scale. A 30 cm tile is 0.30 m on a side, not 30, so you must convert before dividing. This calculator does the conversion for you.
- Forgetting a waste allowance. Buying only the exact number leaves nothing for cuts, breakages, or future repairs. Always add at least 10%, and more for diagonal or patterned layouts.
- Rounding tiles down. Tiles can only be bought whole, so the count must be rounded up. Rounding 222.2 down to 222 leaves part of the floor uncovered.
- Mixing batches (dye lots). Tiles from different production batches can differ slightly in shade. Buy enough in one order, and keep a few spares from the same batch for later repairs.
- Tiling over the full room area on walls. For walls, measure the actual tiled area, not the whole wall. Subtract large openings like windows or a mirror so you do not over-order.
Glossary
- Waste allowance
- Extra tiles added as a percentage to cover cutting, breakages, and spares for future repairs. Typically 10% for simple layouts.
- Tile area
- The surface one tile covers, found by multiplying its length by its width once both are in the same unit as the room.
- Tiles per box
- How many tiles come in one box, printed on the packaging. Used to convert a tile count into a number of boxes to buy.
- Dye lot (batch)
- A single production run of tiles. Tiles from different lots can vary slightly in colour, so it pays to buy from one lot.
- Large-format tile
- A tile larger than about 15 in (38 cm) on one side. These produce bigger offcuts, so a higher waste allowance is wise.
Frequently asked questions
How many tiles do I need?
Divide the area you are covering by the area of one tile, add a waste allowance (usually about 10%), and round up to whole tiles. For example, a 20 sq m floor with 0.09 sq m tiles needs 20 ÷ 0.09 = 222.2, then × 1.10 and rounded up to 245 tiles. This calculator does the full sum for you.
How much waste should I add for tiles?
A 10% allowance suits a straight (grid) layout in a simple room. Use 15% for a diagonal layout and 15% to 20% for herringbone or other complex patterns, for large-format tiles, or for a room with many corners and cuts. First-time DIY installers should add a little extra on top.
How do I calculate tiles per box?
Divide the total tiles you need (including waste) by the tiles-per-box figure printed on the packaging, then round up. If you need 132 tiles and a box holds 10, that is 132 ÷ 10 = 13.2, rounded up to 14 boxes. Enter the tiles per box here and the calculator works out the boxes automatically.
Does this tool work for both floor and wall tiles?
Yes. The maths is identical: you are covering an area with tiles of a known size. For a wall, just measure the area you are actually tiling and subtract large openings such as windows or a mirror before entering the figure.
Why does the calculator round up?
You cannot buy a fraction of a tile, so any partial tile means buying one more. Rounding up after adding waste guarantees you have enough to finish the job and a few spares for cuts and future repairs.
What assumptions does this calculator make?
It assumes a rectangular area, tiles laid in a regular grid, and that grout joints are thin enough to ignore for counting purposes. It does not subtract for fixtures unless you reduce the area yourself, and it does not account for unusually large grout gaps, which would slightly lower the count.