How to use the tile calculator calculator
- 1
Measure the area to be tiled
Add a section for each area. A bathroom floor plus a shower surround is several sections, since the walls and the floor are measured separately and may use different tiles.
- 2
Enter the tile size
Use the face dimensions of the tile you are buying. Nominal tile sizes often differ slightly from actual ones, so measure a tile if you have one.
- 3
Enter the grout joint
Enter the joint width you are working to. It is added to both dimensions, because each tile occupies its face plus one joint along each edge.
- 4
Choose an allowance for the layout
A square layout in a rectangular room cuts along two edges. A diagonal layout cuts at every edge and corner. Pick a percentage that matches the pattern you are laying.
- 5
Add your pricing
Enter your price per tile for an estimated total. Tile is often sold by the box or by the square foot, so check what a single unit price covers.
Formula
Tiles = area(sq ft) / (((length + joint) / 12) x ((width + joint) / 12))
The joint is added once to each dimension, since each tile carries one joint along each of two edges in the repeating pattern.
Worked example
A 200 square foot floor using 12 by 12 inch tiles with a 0.125 inch grout joint
- 1Module size: 12.125 by 12.125 inches.
- 2Module area: (12.125 / 12) x (12.125 / 12) = 1.0209 square feet.
- 3Tiles per square foot: 1 / 1.0209 = 0.98.
- 4Tiles for the floor: 200 / 1.0209 = 196.
The floor takes 196 tiles before any allowance. Without the grout joint the figure would be 200, so the joint saves four tiles here.
Worked examples
Smaller tiles, same floor
The same 200 square feet using 6 by 6 inch tiles with the same joint
- 1Module size: 6.125 by 6.125 inches.
- 2Module area: (6.125 / 12)^2 = 0.2605 square feet.
- 3Tiles per square foot: 1 / 0.2605 = 3.84.
- 4Tiles for the floor: 200 / 0.2605 = 768.
Smaller tiles need many more pieces and produce far more grout line. The joint also matters more proportionally: on a 6 inch tile it adds 2 percent to each dimension, against 1 percent on a 12 inch tile.
Allowing for a diagonal layout
The 196 tile floor laid on a 45 degree diagonal
- 1Base count: 196 tiles.
- 2A diagonal layout cuts along all four edges and at every corner.
- 3Choosing a 15 percent allowance: 196 x 1.15 = 225.4.
- 4Round up: 226 tiles.
The 15 percent here is a figure chosen for this example, not a published rate. Diagonal layouts genuinely waste more, and the right figure depends on the room shape.
How the grout joint affects the count
Each tile occupies its own face plus the grout line around it. In a repeating grid, that works out to one joint width added along each dimension, so a 12 inch tile with an eighth inch joint repeats every 12.125 inches.
Unlike brick, where the joint is a large fraction of the unit height, tile joints are usually small relative to the tile. On a 12 inch tile an eighth inch joint changes the count by about 2 percent. On a 6 inch tile the same joint changes it by about 4 percent, because the joint is proportionally larger.
So the joint matters more for small tiles and mosaics than for large format ones. It is worth entering either way, but getting it slightly wrong on a large tile will not distort the estimate.
Layout drives the waste
The single biggest variable in a tile order is not the area or the tile size but how the tile is laid. A straight grid in a rectangular room cuts along two edges, and many of those cut pieces can start the opposite side.
A diagonal layout cuts along all four edges and leaves triangular offcuts that rarely fit anywhere else. A running bond offsets each row, so the cut at one end of a row does not match the next. A room with alcoves, a curved edge, or a fireplace hearth cuts continuously around each obstruction.
Large format tiles amplify all of this, because each cut wastes more material. A cut across a 24 inch tile discards far more than a cut across a 6 inch one, even though the cut line is the same.
This is why the allowance is a judgment rather than a rate. Look at the layout drawing, count roughly how many edges will be cut, and choose accordingly.
Buying in boxes and matching batches
Tile is normally sold by the box, with each box covering a stated area. That means the practical order rounds up to a whole box rather than a whole tile, so a count of 226 tiles may become however many boxes cover that.
It is also worth ordering the whole quantity at once. Tile is produced in batches, and colour can shift slightly between them, so a later top-up order may not match what is already down. That is a stronger argument for a generous allowance than the cutting waste is.
Keeping a few spare tiles after the job is finished is common practice for the same reason. Replacing a cracked tile years later from the original batch is far easier than trying to match one.
Common mistakes
Where tile counts go wrong:
- Ignoring the grout joint, which matters most on small tiles.
- Using a nominal tile size when the actual tile is slightly different.
- Applying a straight-layout allowance to a diagonal or offset pattern.
- Forgetting that large format tiles waste more per cut.
- Ordering in tiles when the product is sold by the box.
- Topping up later from a different batch and getting a colour mismatch.
- Measuring a shower surround as one area when it is three separate walls.
Sources and methodology
Every figure on this page comes from geometry rather than from a product database. Areas use the standard area formulas, counts divide an area by the size of one unit, and unit conversions use exact factors: 12 inches to a foot, 9 square feet to a square yard, and 100 square feet to a roofing square.
YardCalc publishes no product dimensions, coverage rates, or prices. Unit sizes differ between manufacturers and regions, and a figure that is right for one product is wrong for another, so the calculator asks you for the size of the product you are actually buying. Prices are yours alone.
Results are planning estimates, not order quantities. Read how every value on the site is derived and checked in the YardCalc calculation methodology.
Tiles per square foot by tile size
Worked arithmetic at a 0.125 inch grout joint over a 200 square foot area, with no allowance added. These sizes demonstrate the calculation rather than recommending a product.
| Unit face size | Module with joint | Units per sq ft | Units for 200 sq ft |
|---|---|---|---|
| 4 x 4 in | 4.13 x 4.13 in | 8.46 | 1,693 |
| 6 x 6 in | 6.13 x 6.13 in | 3.84 | 768 |
| 12 x 12 in | 12.13 x 12.13 in | 0.979 | 196 |
| 18 x 18 in | 18.13 x 18.13 in | 0.438 | 88 |
| 24 x 12 in | 24.13 x 12.13 in | 0.492 | 99 |
| 24 x 24 in | 24.13 x 24.13 in | 0.247 | 50 |
Frequently asked questions
- How many tiles do I need?
- Divide the area by the size of one tile plus its grout joint. A 200 square foot floor in 12 by 12 inch tiles with an eighth inch joint takes 196 tiles before any allowance for cuts.
- How many 12x12 tiles in 100 square feet?
- With an eighth inch grout joint, 98 tiles. Laid with no joint at all it would be exactly 100. Add an allowance on top for cuts and breakage.
- Does the grout joint really matter?
- It matters more for small tiles. On a 12 inch tile an eighth inch joint changes the count by about 2 percent; on a 6 inch tile the same joint changes it by about 4 percent. Enter it either way.
- How much extra tile should I buy?
- There is no single figure. A straight layout in a plain rectangle needs little; a diagonal layout, an offset pattern, or a room with alcoves and curves needs considerably more. Large format tiles also waste more per cut. Judge it from your layout.
- Should I order all the tile at once?
- Generally yes. Tile is made in batches and colour can shift between them, so a later top-up may not match. Ordering the full quantity together, and keeping a few spares, avoids that.
- Does this include grout and adhesive?
- No. Those depend on the tile size, joint width, and substrate rather than the tile count, so they are separate estimates.
Tile counts divide your measured area by the module area, which is the tile face you enter plus the grout joint you enter. No tile size, joint width, layout allowance, or price is assumed. Counts come from exact geometry using the product dimensions you enter. Confirm the product size, the layout, cutting and breakage, and the final order quantity with your supplier before purchasing.
Results are planning estimates. Last reviewed 2026-08-30.