Sheet goods are not priced by area
Pricing panel goods by square metre with a waste factor understates a one-off job by roughly a fifth, because board is bought in whole sheets and the offcut is yours whether you use it or not. Nesting the job onto real sheets and counting them is the only estimate that matches the invoice.
The usual method, and where it goes wrong
The common way to price board is to add up the area of the parts, multiply by a rate per square metre, and add a waste factor — 10 or 12 per cent is the number most spreadsheets carry. It is quick, it is defensible, and on a long production run it is roughly right.
On a one-off it is not. Your supplier does not sell you 4.2m² of melamine; they sell you two 2500×1250 sheets and hand you the offcut. Whether that offcut becomes a shelf next month or firewood, you paid for it on the day. A 12 per cent waste allowance quietly assumes the offcut is somebody else's problem.
What whole-sheet counting does to the number
Nest the same three jobs onto real sheets with a real kerf and edge trim, count the sheets, and the board line rises — by a fifth on a good job, by far more on a small one where the parts fit badly:
| Job | Sheets | Utilisation | What drives it |
|---|---|---|---|
| Three-module run, 2900mm | 11 | ~79% | Long sides pack well; fronts waste the rest of the sheet |
| One 1000mm wardrobe | 8 | ~60% | Three materials, each needing its own sheets |
| 800mm cabinet, two rails | 4 | ~55% | One cabinet cannot fill a sheet of anything |
Utilisation is the honest measure of a small job: at 55 per cent you are paying for nearly half a sheet of nothing, several times over. No waste factor expresses that, because the shortfall is not proportional to the parts — it is proportional to how many different materials the job touches.
Three consequences worth acting on
Fewer materials beats clever nesting
Every distinct decor and thickness opens its own sheet. A design in two materials rather than four will usually beat any nesting improvement you can make within four.
Tall runs pull a bigger sheet
A 2600mm side panel cannot come off a 2500mm sheet. Above about 2480mm of run height the carcass material jumps to the 3050mm sheet — a real step in price that a per-square-metre rate hides completely.
Ask your supplier for their actual sizes
Sheet sizes are not universal: 2500×1250 and 3050×1250 are common in Belgium, 2800×2070 elsewhere in the trade, 8×4ft and 5×5ft in North America. A decor sold in only one size changes the nest and the price. Price each panel on the sizes it is really sold in, not on a house standard.