How much tile waste should you allow for?
10% extra is the standard for a straight lay in a normal room. Go to 15% for diagonal, 20% for herringbone, and higher still for small tiles or a room full of corners.
Waste is not the same as error. Most of the tile you throw away was never a mistake — it was the unavoidable end of a row, or the triangle cut off the edge of a diagonal layout. Understanding where it comes from is what lets you pick a sensible percentage instead of guessing.
Where the waste actually goes
- Perimeter cuts. Almost no room is an exact multiple of the tile width, so the last row in each direction is a rip cut. That is one whole tile consumed per row.
- Obstacles. Toilets, floor registers, radiator pipes, door jambs, a shower curb — each one interrupts a tile and leaves a piece too small to reuse.
- Layout alignment. Patterns force tiles to start at fixed points. Centring a pattern or aligning it with a doorway can mean cutting both ends of the room.
- Breakage. Shipping damage, a chipped edge from the wet saw, a tile dropped during handling. Plan on losing two or three tiles on any job.
- Defects. Warped or badly rectified tiles get rejected during installation. The cheaper the tile, the more often this happens.
Waste factor by layout
| Situation | Waste | Example |
|---|---|---|
| Square room, straight lay, few cuts | 5% | New-build closet |
| Normal room, straight lay | 10% | Bedroom, kitchen, hallway |
| Two or more connected rooms | 12% | Open-plan kitchen and dining |
| Diagonal lay, 45° | 15% | Bathroom with a feature layout |
| Small tiles, under 6 in | +5% on top | Hexagon or penny tile |
| Herringbone or chevron | 20% | Entry hall, feature floor |
| Many obstructions | +3–5% on top | Utility room, bathroom |
Worked example
A 12 × 12 ft bathroom is 144 sq ft. It has a toilet, a vanity, a floor register and a doorway, and it will be laid straight.
- Floor area: 12 × 12 = 144 sq ft
- Waste at 10%: 144 × 1.10 = 158.4 sq ft
- Tile: 12 × 24 inch, 2 sq ft each → 158.4 ÷ 2 = 79.2, so 80 tiles
- Boxes: 6 tiles per box → 80 ÷ 6 = 13.3, so 14 boxes
- Spare: buy 15 boxes, keep one sealed
Notice how the rounding compounds. Without waste the room needs 12 boxes; with waste and a spare box you buy 15. That extra 25% is not waste — 10% is, and one box is insurance. Run the same numbers in the tile calculator if you want to check the arithmetic.
The one subtraction that matters
Subtract things that permanently occupy the floor: a bathtub, a shower pan, a built-in kitchen island. Do not subtract a vanity, a toilet or a washing machine — tile should run underneath them, because replacing a vanity later without a tile patch is far more expensive than the 6 sq ft of tile you saved.
If you do subtract a large item like a tub, add 5% back on top of the reduced area. The layout around a tub produces more diagonal cuts than a clean rectangle, and the calculator will under-read the true consumption.
Why the spare box is not optional
Tile is a fired product. Each production run is a dye lot, and colours shift slightly between lots even on the same sku. If a tile cracks in two years — a dropped pan, a furniture leg, a hairline crack over a subfloor joint — a replacement box from a new lot will be visibly different in a floor that is lit from one side.
Keep one unopened box, stored flat, dry and off the concrete. Do not stack heavy things on it. Write the room name on the carton with a marker so future-you knows which floor it belongs to.
There is a second reason to keep it unopened: return policies. Most tile retailers accept unopened boxes for 30–90 days. If the job finishes and you did not need the spare, you get your money back — but if you opened all the boxes on day one, you own them forever.
Five waste mistakes
- Applying waste after rounding. Add the percentage to the area first, then convert to tiles, then to boxes. Rounding at each step inflates the total by a box or two.
- Using 10% for a diagonal layout. Every perimeter tile in a 45° lay is a triangle, which means the offcut is almost never usable. Budget 15%.
- Forgetting the closet. If you are tiling into a closet, it is a separate rectangle with its own four walls of cuts.
- Buying exactly the computed amount. A single broken tile on the last row sends you back to the store for a box from a different lot.
- Mixing dye lots. If you do need extra, check the lot number on the carton. Most stores will let you order from the same lot if you ask early.
Frequently asked questions
Is 10% enough waste for tile?
For a straight lay in a rectangular room with one or two doorways, yes — 10% is the standard and rarely leaves you short. It is not enough for diagonal layouts, herringbone patterns, rooms with many corners, or small tiles under 6 inches, where 15–20% is more realistic.
Should I buy 10% or 15% extra tile?
Buy 10% extra for the installation and then add one full box on top as a spare. The 10% is consumed by cuts during the job; the extra box stays sealed for future repairs. If the room is small, one box may already be more than 10% — simply buy two boxes over the calculated quantity.
Does tile waste include breakage?
Yes, in practice. Manufacturers report 2–5% breakage in a normal shipment, and a careless cut can destroy a tile. The waste allowance absorbs both. Inspect the pallet before you leave the store — shards in a sealed box mean the whole box has been dropped.
Can I return leftover tile?
Usually yes, if the boxes are unopened and you return them within 30–90 days with the receipt. That is exactly why you should keep one extra box unopened: it is returnable for months, and if you never need it, you get the money back. Opened boxes are almost never accepted.
How much tile should I keep for repairs?
One full box, sealed, stored flat and dry. Tile is fired in dye lots, and the same sku bought two years later will usually be a slightly different shade. A box of 12 × 24 porcelain is roughly $40–$70 — cheap compared to re-tiling a room because a single tile cracked.