Tile Calculator
Tiles and boxes needed for a floor or wall, allowing for grout gaps and cutting waste.
The area
The tile
Common sizes
This works out how many tiles a floor or wall needs, including a waste allowance sized to your layout.
It handles any tile size and converts between tile count, boxes and square footage.
How many tiles a room needs
Tile quantity is area divided by tile area, plus waste. A 200 sq ft floor in 12 × 12 in tiles needs 200 tiles before waste; in 6 × 6 in tiles, each covering a quarter of a square foot, it needs 800.
The waste allowance is where judgement comes in, and a flat 10% is not always right. 10% suits a straight layout in a simple rectangular room. 15% is needed for diagonal or herringbone patterns, which generate far more cut tiles, and for rooms with many corners and obstructions.
The thing that turns a shortfall into a real problem is dye lots. Tiles are produced in batches and colour varies noticeably between them. A top-up order weeks later frequently does not match, so order the whole job at once, including the waste.
Halving the tile dimension quadruples the count, because area scales with the square. A diagonal layout would take the 12-inch job to 230.
What to enter
- Area to tile
- In square feet. Length × width, or the sum of several rectangles for an irregular space.
- Tile size
- In inches. A 12 × 12 tile covers 1 sq ft; a 6 × 6 covers 0.25; an 18 × 18 covers 2.25.
- Layout
- Straight, diagonal or herringbone. Diagonal and herringbone create many more cut tiles and need more waste.
- Waste percentage
- 10% for straight layouts in simple rooms, 15% for diagonal, herringbone or complex shapes.
Tile coverage per unit
- 6 × 6 in
- 0.25 sq ft each. Four tiles per square foot.
- 12 × 12 in
- 1.0 sq ft each. The simplest case.
- 18 × 18 in
- 2.25 sq ft each.
- 24 × 24 in
- 4.0 sq ft each. Fewer grout lines, and much less forgiving of an uneven subfloor.
- Subway 3 × 6 in
- 0.125 sq ft each. Eight per square foot, and usually laid in a running bond.
What this assumes
Grout lines are not deducted. They are a small fraction of the area and the waste allowance covers them.
Waste percentages are typical. Very complex rooms, large-format tiles and patterned layouts can all need more.
How to calculate the tiles you need
Area divided by tile area, then add waste, then round up to whole boxes.
- 144
- Square inches in a square foot
- waste
- 0.10 straight, 0.15 diagonal or complex
Measure the area. Length × width, adding the sections of an irregular room together.
Work out the coverage of one tile. Multiply its dimensions in inches and divide by 144. A 6 × 6 tile is 36 ÷ 144 = 0.25 sq ft.
Divide and add waste. 200 ÷ 0.25 = 800 tiles, then × 1.10 = 880.
Round up to whole boxes and order at once. Order the full quantity in one go so it comes from the same dye lot. A later top-up may not match.
See a worked example: the same floor, two tile sizes
- Area
- 200 sq ft
- Layout
- Straight, so 10% waste
12 × 12 in tiles: 1 sq ft each, so 200 tiles, 220 with waste.
6 × 6 in tiles: 0.25 sq ft each, so 800 tiles, 880 with waste.
Halving the tile dimension quadruples the count, since area goes as the square of the side.
Switching the 12-inch job to a diagonal layout raises the waste to 15%, so 230 tiles rather than 220.
220 tiles at 12 in, 880 at 6 in
Frequently asked questions
10% for a straight layout in a simple rectangular room. 15% for diagonal or herringbone patterns, or rooms with many corners and obstacles.
Buy a few extra beyond that for future repairs. A cracked tile in five years is easy to replace if you kept spares and nearly impossible to match if you did not.
Tiles are made in production batches, and colour varies subtly between them. Tiles from different lots can look noticeably different once laid.
Order the whole job at once, including waste, and check the lot number on every box. This is the single most common reason a tiling job ends up with a visible patch.
No, and it works out fine. Grout lines are a small fraction of the area, and ignoring them errs slightly high, which is the safe direction.
The waste allowance more than covers the difference. Nobody sizes a tile order by grout width.
Because every tile meeting a wall has to be cut at an angle, and the offcuts are usually unusable. A straight layout produces far fewer cuts and more reusable pieces.
Herringbone is more wasteful still. 15% is the usual allowance for both, and 20% is not unreasonable for a complicated room.
The same way, using wall area instead of floor area: height × width, minus any window or fixture openings.
For a shower surround, calculate each wall separately and add them. Do not forget the niche if there is one, since its interior faces need tile too.
Coverage depends on trowel size and tile format. Thin-set typically covers 80-100 sq ft per 50 lb bag with a quarter-inch notched trowel, and less with larger tiles needing a bigger notch.
Grout depends on tile size and joint width. Larger tiles need much less grout per square foot, since there are fewer joints. The bag will state coverage for common combinations.
Problems people actually run into
Ordering exactly the area
200 tiles for a 200 sq ft floor leaves nothing for cuts, breakages during handling, or a spare for future repairs.
Every edge tile is cut, and cuts produce waste. 10% is the minimum sensible allowance and 15% for anything but a plain straight layout.
Topping up mid-job
Running short means a fresh order, and a fresh order usually means a different dye lot. The difference is often invisible in the shop and obvious on the floor.
Order everything at once and check that all boxes share a lot number before starting.
Results are estimates for general information only and are not professional financial, medical, or legal advice. Read our full disclaimer.
Last updated: September 4, 2026