Waste factor reference table
How much extra material to order, by what you are laying and how you are laying it — and why the usual flat 10% is wrong more often than it is right.
Quick answer
Total waste is three additions, not one number: the pattern's own cutting loss, an addition for how complicated the room is, and an addition for small rooms where a single ruined cut is a large share of the order. Straight-laid tile starts at about 10%, diagonal 15% and herringbone 18%, before those two adjustments.
The short version
Waste is not caused by the room. It is caused by cuts. Every piece of material that meets a wall, a door frame, a corner or a pipe gets cut, and most offcuts cannot be used anywhere else. A layout that forces more cuts per square metre wastes more material, and the amount is predictable enough to put in a table.
The allowance used across this site is built from three separate additions, not one number:
total waste = pattern waste + room-shape addition + small-room addition
They add rather than multiply, because they describe independent causes. A herringbone floor in a complicated small bathroom really does need about 18 + 5 + 4 = 27% extra, and anyone who has run short 80% of the way through one will tell you that figure is not padded.
Tile patterns
| Pattern | Waste | Why |
|---|---|---|
| Straight / stack bond | 10% | Cuts occur only at the perimeter, and an offcut from one edge often serves the opposite edge. |
| Brick bond, 50% offset | 11% | Alternate rows start with a half tile, which is a cut — but the other half is usually usable. |
| Brick bond, 1/3 offset | 12% | Three-row repeat means two of every three row-starts are cuts, and the remainders match less often. |
| Diagonal 45° | 15% | Every perimeter tile becomes a triangle. Two triangles rarely make one usable tile because the cut runs the wrong way. |
| Basketweave | 15% | The module has to land whole; anything that does not fit the module at the edge is scrap. |
| Modular / multi-size | 15% | You must buy sizes in the ratio the pattern needs, not the ratio the room needs, so some sizes are left over. |
| Herringbone | 18% | The perimeter is an unbroken run of compound cuts, and the pattern itself cannot absorb an odd offcut anywhere. |
Plank flooring layouts
| Layout | Waste | Why |
|---|---|---|
| Straight, along the long wall | 8% | The offcut from the end of each row starts the next row, which is also how you get the required stagger. Very little is scrapped. |
| Straight, across the room | 10% | More rows, more end cuts, and the offcuts are shorter so fewer of them are long enough to reuse. |
| Diagonal 45° | 15% | Both ends of every plank are angle cuts against the wall. |
| Herringbone / chevron | 20% | Planks are pre-cut to a fixed module and the perimeter is all compound cuts. Chevron planks are also handed — left and right are not interchangeable. |
Other materials
| Material | Allowance | Notes |
|---|---|---|
| Plasterboard, simple room | 10% | Offcuts around openings are rarely large enough to use elsewhere. |
| Plasterboard, many openings or a stairwell | 15% | Every opening generates two unusable offcuts. |
| Concrete, poured into formwork | 5% | Formwork is accurate; the loss is spillage and what stays in the barrow. |
| Concrete, poured against excavated earth | 10% | Trench sides slump and the base is never flat. Always measure the trench you dug, not the one you set out. |
| Carpet | 10–15% | Sold in fixed roll widths, so waste is set by how your room divides into that width, not by a percentage. Plan the cuts. |
| Sheet vinyl | 10% | As carpet, plus a pattern-repeat allowance if it has one. |
| Skirting and trim | 10% | Mitres eat length, and a mis-cut mitre costs a whole length rather than a little. |
| Paint | 0% | Paint has no cutting waste. What it has is an absorption penalty on the first coat — a different problem, covered in the coverage rates. |
The room-shape addition
| Room | Add | Description |
|---|---|---|
| Simple | 0% | A rectangle with square corners. One doorway. Nothing in the middle of the floor. |
| Normal | +2% | One or two cut-outs: a WC pedestal, a kitchen island, a chimney breast, a second doorway. |
| Complex | +5% | Several cut-outs, alcoves, a bay, walls that are not square to each other, or anything curved. |
Test for "complex": count the internal corners in the floor outline. A rectangle has none. Each one is a place where two rows of cuts meet and offcuts stop being reusable.
The small-room addition
Waste is usually quoted as a percentage, which quietly assumes the loss scales with the area. It does not. A single ruined cut — a chipped edge, a tile snapped on the wrong side of the line, a plank cut 10 mm short — costs the same one piece whether the room is 3 or 40 square metres. In a small room that one piece is a much bigger share of the order.
| Net area | Add |
|---|---|
| Under 3 m² (32 ft²) — cloakroom, shower enclosure | +6% |
| 3–6 m² (32–65 ft²) — small bathroom | +4% |
| 6–12 m² (65–130 ft²) — bathroom, small bedroom | +2% |
| Over 12 m² (130 ft²) | 0% |
Small rooms also have a higher ratio of perimeter to area, which is the same thing said differently: proportionally more of the floor is made of cut pieces.
Three worked examples
A 12 m² kitchen floor, 600 × 600 porcelain, straight
10% pattern + 2% shape (island and two doorways) + 2% small room = 14%. Order 13.7 m², which at 4 tiles per box rounds to 10 boxes and gives you 14.4 m².
A 4 m² bathroom floor, 300 × 300, diagonal
15% pattern + 5% shape (WC, basin pedestal, awkward corner) + 4% small room = 24%. On 4 m² that is under a square metre of extra tile — roughly the price of a takeaway, against the certainty of a shade mismatch if you run out.
A 28 m² living room, laminate, straight along the long wall
8% pattern + 0% shape + 0% small room = 8%. This is the case where the flat 10% rule over-orders, and on a big floor that is a real amount of money. Ordering by pattern rather than by rule of thumb saves roughly half a pack here.
Why the direction of the error matters. Over-ordering costs you the price of the surplus and gives you repair stock. Under-ordering costs you a second delivery, a likely batch mismatch in shade, and sometimes the whole job re-done. The two errors are not symmetrical, which is why every figure in this table is rounded up rather than down.
When to ignore the table entirely
- Material you cannot re-order. Clearance stock, a discontinued line, reclaimed brick or timber, anything imported one-off. Buy every piece you can afford at the time of the first order.
- Roll goods. Carpet, sheet vinyl, wallpaper. Waste depends on how your room divides into the roll width or the pattern repeat, and can be anywhere from 5% to 40%. A percentage is meaningless here; lay the cuts out on paper.
- Your first time. If you have never cut this material before, add 5%. You will break some learning, and that is a cheaper way to learn than running out.
- Tile with a strong directional pattern or heavy shade variation. You will reject pieces on appearance as well as on fit. Add 5%.
Use it
Every calculator on this site applies these figures automatically once you pick the pattern and room shape:
- Tile calculator — applies every figure on this page
- How many tiles do I need? — the same numbers precomputed at common areas
- Flooring calculator
- Plasterboard calculator
- Concrete calculator
Last reviewed 2026-10-17. These allowances are our own working figures, assembled from merchant estimating practice and manufacturer fitting guidance, and are deliberately rounded up. They are planning estimates, not a guarantee.
Sources and confidence
Every figure used on this page, what kind of figure it is, and where it came from. Figures marked as working estimates have no single authority behind them — they are the ones to check against your own supplier.
| Figure | Kind | Source | Note |
|---|---|---|---|
| Pattern waste percentages | Working estimate | no primary source consulted | Merchant estimating practice and fitting guidance, rounded up. The weakest figures on the site and the ones most worth arguing with. |
| Waste is additive: pattern + room shape + small room | Derived | The model itself | A stated modelling choice, not a measured fact. Set out in full on this page. |
| Small-room addition thresholds (under 6 m², under 12 m²) | Working estimate | no primary source consulted | Chosen so that one ruined full tile stays inside the allowance. |
Derived Calculated from geometry. The formula is on this page. Published From a manufacturer data sheet or published standard, cited below. Working estimate Trade practice, rounded up. No single authority; the weakest category here.