Home
How To Calculate Tile Count
Tile count is the surface area divided by the area of one tile, with a wastage allowance added and the answer rounded up. The only real decisions are how much wastage to allow and which direction to round.
Quick Answer
Tiles = (room area / tile area) x (1 + wastage)
- A
- Area to be covered, in square metres
- a
- Area of one tile, in the same square unit
- w
- Wastage rate as a decimal, commonly 0.1 for ten percent
- N
- Tiles to order, rounded up to a whole number
Divide the area you must cover by the area of a single tile, then add a wastage margin. A room 4 metres by 3 metres is 12 square metres; a 0.3 metre square tile is 0.09 square metres; and 12 / 0.09 = 133.33333333333334 exact tiles. With ten percent wastage that becomes 133.33333333333334 x 1.1 = 146.66666666666669 tiles, which rounds up to 147 tiles to order. The wastage covers edge cuts, awkward corners and breakages, and the final round is always upward because you cannot buy a fraction of a tile.
What Is Tile Count?
Tiles are sold by the piece, not by the square metre, so any flooring or walling project begins by turning an area into a count. The arithmetic is a single division: divide the surface area you must cover by the area of one tile. A room of 12 square metres tiled with 0.09 square metre tiles needs 133.33333333333334 of them before any allowance is made. Because the answer is rarely a whole number, the count has to be rounded up and a wastage margin added before you order.
Take a floor 4 metres long and 3 metres wide. Multiplying the two dimensions gives 12 square metres, which is the area to be covered. A square tile measuring 0.3 metres on each side has an area of 0.3 x 0.3 = 0.09 square metres. Dividing 12 by 0.09 gives 133.33333333333334, the exact number of tiles the floor would consume if every tile could be used whole and nothing were ever wasted.
The exact figure of 133.33333333333334 is a mathematical ideal rather than an order quantity. Real tiling loses tiles to edge cuts, awkward corners, breakages in transit and the occasional mis-cut, so a wastage allowance is added before buying. A common allowance is ten percent, which here means multiplying 133.33333333333334 by 1.1 to reach 146.66666666666669 tiles. That extra margin is not padding for its own sake; it is the difference between finishing the job and returning to a shop that no longer stocks your batch.
Once the wastage-adjusted figure is in hand, round it up to the next whole tile and never down. You cannot buy 146.66666666666669 tiles, and rounding down to 146 would leave the job short by a fraction that no shop can supply. The rule is asymmetric on purpose: a little surplus is cheap and harmless, while a shortage mid-project forces a second trip and risks a colour or batch mismatch. Round up, keep the leftovers, and treat them as insurance rather than waste.
Tile size interacts with the room dimensions in a way the pure area calculation hides. If a 4 metre wall is tiled with 0.3 metre tiles, 4 / 0.3 = 13.333333333333334 tiles fit along it, so a full row leaves a narrow offcut column. Those offcuts still cost a whole tile each, which is why the area method is a lower bound rather than the last word. Long, thin tiles and small rooms with many obstructions both push the true count above the plain area figure.
Grout lines and pattern direction change the count in ways that are easy to overlook. A 3 millimetre grout joint adds a little to the effective footprint of each tile, so a run of many tiles drifts away from the ideal count; the effect is small per tile but compounds across a large floor. Pattern direction matters even more: a herringbone or diagonal layout produces more offcuts than a straight grid, and tiles with a directional grain cannot be rotated to rescue a short offcut. Both effects argue for a larger wastage allowance, commonly fifteen percent rather than ten.
Ordering usually happens by the box, not by the individual tile, so a final conversion is needed. If tiles come in boxes of ten, the 146.66666666666669-tile estimate becomes 147 tiles, which is fifteen boxes with three tiles left over. Buying by area alone, without this step, is how projects end up one box short. Always read the pack quantity before translating a tile count into a purchase, and check whether the retailer sells single tiles as well as sealed boxes.
Units must stay consistent throughout. If the room is measured in metres, the tile side must be in metres too, so a 300 millimetre tile is entered as 0.3 metres and not as 300. Mixing metres with millimetres turns 0.09 square metres into 90000 square metres and inflates the tile count by a factor of a million. Convert everything to one unit before dividing, and the division will behave.
Two habits keep the answer reliable. First, add wastage only once, at the end, after the exact division, because adding it earlier compounds through the arithmetic and inflates the result. Second, round up rather than to the nearest whole number, and record the exact decimal somewhere in case the supplier asks how it was reached. The whole method is one division and one multiplication: 12 / 0.09 = 133.33333333333334, then 133.33333333333334 x 1.1 = 146.66666666666669, and 147 tiles to order.
Formula
A = L x W
Length times width, with both measurements in one consistent unit. Subtract permanent obstructions only if they will never be tiled behind.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| L | Room length | length | One side of the floor or wall, in metres. It is 4 in the worked example. |
| W | Room width | length | The perpendicular side, in the same unit. It is 3 in the worked example. |
| A | Area to be covered | square units | 4 x 3 = 12 square metres for the worked room. |
a = s x s
For a square tile, multiply the side by itself. Rectangular tiles use length times width instead, so a 0.3 by 0.6 metre tile covers 0.18 square metres.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| s | Tile side | length | 0.3 metres for a 300 millimetre square tile. |
| a | Area of one tile | square units | 0.3 x 0.3 = 0.09 square metres. |
N = (A / a) x (1 + w)
Divide the surface area by the tile area, then multiply by one plus the wastage rate written as a decimal. Round the result up to a whole tile.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| N | Tiles to order | count | 12 / 0.09 = 133.33333333333334 exact tiles before wastage, and 146.66666666666669 after it. |
| A | Surface area to cover | square units | 12 square metres in the worked example. |
| w | Wastage rate | decimal | Ten percent, entered as 0.1, which lifts the count to 146.66666666666669 tiles. |
How To Calculate Tile Count
- 1
Measure the surface in one consistent unit
Measure the length and width of the floor, or the height and width of the wall, and write both down in the same unit. A room 4 metres by 3 metres gives 4 and 3. If the tape reads in centimetres, convert to metres first, because the tile side will be quoted in metres and the two figures must agree before any division is attempted.
- 2
Multiply to get the area to be covered
Multiply length by width to get the surface area: 4 x 3 = 12 square metres. If the space is not a simple rectangle, split it into rectangles, compute each one and add the results. Subtract the areas of permanent obstructions such as fitted units or a fixed bath only if they will never be tiled behind.
- 3
Compute the area of a single tile
Multiply the tile side by itself for a square tile: 0.3 x 0.3 = 0.09 square metres. Rectangular tiles use length times width instead, so a 0.3 by 0.6 metre tile covers 0.18 square metres. Write this figure down separately, because it is the divisor for the next step and the most common place for a unit slip.
- 4
Divide the surface area by the tile area
Divide the surface area by the area of one tile: 12 / 0.09 = 133.33333333333334. That decimal is the exact number of tiles the geometry demands, with no allowance for cuts or breakage. Keep the full value rather than rounding it here, because rounding too early carries the error into the wastage multiplication that follows.
- 5
Add wastage, then round up to a whole tile
Multiply the exact count by one plus the wastage rate: 133.33333333333334 x 1.1 = 146.66666666666669 for ten percent. Round that up to 147 tiles, never down, and convert to boxes if the tiles are sold in packs. Order the rounded figure and keep the surplus tiles for future repairs.
Examples
Example 1: The area of a 4 m by 3 m floor
- Room length
- 4 m
- Room width
- 3 m
| Step | Calculation | Result |
|---|---|---|
| Length times width | 4 x 3 | 12 |
| Same floor in square centimetres | 12 x 10000 | 120000 |
Result: A 4 m by 3 m floor covers 12 square metres, which is 120000 square centimetres, and that 12 square metres is the area every later step divides by.
Example 2: The area of one 0.3 m square tile
- Tile side
- 0.3 m
| Step | Calculation | Result |
|---|---|---|
| Tile side multiplied by itself | 0.3 x 0.3 | 0.09 |
| Same tile in square centimetres | 0.09 x 10000 | 900 |
Result: One 0.3 m square tile covers 0.09 square metres, which is 900 square centimetres, and this tile area is the divisor for the tile count.
Example 3: From floor area to tiles to order
- Room area
- 12 square metres
- Tile area
- 0.09 square metres
- Wastage
- 10 percent
| Step | Calculation | Result |
|---|---|---|
| Exact tiles with no allowance | 12 / 0.09 | 133.33333333333334 |
| With ten percent wastage | 133.33333333333334 x 1.1 | 146.66666666666669 |
Result: The exact count is 133.33333333333334 tiles; with ten percent wastage you need 146.66666666666669, which rounds up to 147 tiles to order.
Calculator
Tiles to order with wastage
146.6667
- Room area in square metres
- 12
- Area of one tile in square metres
- 0.09
- Exact tiles without wastage
- 133.3333
Values update as you type. This calculator covers the single scenario its formula assumes — see Common Mistakes for what it leaves out.
Prefer a full-width tool? Open the Tile Count calculator page.
Common Mistakes
Forgetting the wastage allowance entirely
The exact division gives 133.33333333333334 tiles, and ordering that many ignores every cut and breakage. Add at least ten percent, which here means 146.66666666666669 tiles and a rounded order of 147. A job ordered to the exact area figure almost always runs short near the end, when the offcut tiles are the ones being used.
Rounding down instead of up
You cannot buy a fraction of a tile, so 133.33333333333334 must become 134, and 146.66666666666669 must become 147. Rounding to the nearest whole number, or down, leaves the job short. The only safe direction is up, because a spare tile is trivial next to the cost of a second trip and a possible batch mismatch.
Mixing units between the room and the tile
A room measured in metres with a tile side quoted in millimetres breaks the division. A 300 millimetre tile is 0.3 metres, with an area of 0.09 square metres; entering 300 as the side gives an area of 90000 and a tile count a million times too large. Convert both measurements to one unit before dividing, not after.
Assuming the area calculation is the true tile count
Area alone ignores offcuts. A 4 metre run tiled with 0.3 metre tiles needs 4 / 0.3 = 13.333333333333334 tiles, so the last column in each row is cut and its offcut wasted. Obstructions, diagonal patterns and border tiles all increase the real count beyond the plain area figure, which is exactly why the wastage margin exists.
Adding wastage before the division or compounding it twice
Wastage is a single multiplication applied once, at the end: 133.33333333333334 x 1.1 = 146.66666666666669. Applying it to the room area first, or applying it again to the wastage-adjusted figure, inflates the order well beyond what the job needs. Compute the exact count, then add wastage exactly once, then round.
FAQ
How much wastage should I allow for tiles?
Ten percent is the common default and is enough for a simple straight grid in a regular room, which for 133.33333333333334 exact tiles means 146.66666666666669 and a rounded order of 147. Increase it to fifteen percent for diagonal or herringbone patterns, rooms with many corners, or large-format tiles that are hard to cut cleanly. Keep the surplus tiles for repairs.
Why do I have to round up rather than to the nearest tile?
Because tiles are sold as whole units and a shortfall cannot be solved on site. 146.66666666666669 rounds up to 147, while rounding down to 146 leaves the floor incomplete by the very tiles that are hardest to source later. Rounding up costs one or two extra tiles; rounding down can cost a whole second order and a batch mismatch.
Does tile size change how many tiles I need?
Yes, even for the same floor area. Twelve square metres needs 133.33333333333334 tiles of 0.09 square metres, but only 33.333333333333336 tiles of 0.36 square metres. Larger tiles mean fewer pieces and fewer grout lines, but also more visible offcuts at the edges, so the wastage percentage often rises as the tile gets bigger.
Do grout lines affect the number of tiles?
They affect the layout more than the count. A few millimetres of grout per joint adds up across a long run, so the tiles plus grout may no longer fit an exact number of pieces, forcing more cuts. The area method ignores grout entirely, which is another reason to treat the 133.33333333333334 figure as a minimum rather than a final answer.
How do I convert a tile count into boxes to buy?
Divide the rounded tile count by the number of tiles per box and round up again. With ten tiles a box, 147 tiles means fifteen boxes, since 14.7 rounds to 15. Check the pack size before ordering, because some ranges sell only full boxes while others allow single tiles, and the two give different purchase quantities.
References
- [1]Wikipedia, Tile — https://en.wikipedia.org/wiki/Tile
- [2]Wikipedia, Area — https://en.wikipedia.org/wiki/Area
- [3]Wikipedia, Tessellation — https://en.wikipedia.org/wiki/Tessellation