- Work out the weight: area × thickness × density, at your dated price per kg
- Choose the area you bill: bounding box, share of the nested sheet, or whole sheets
- Add the markup, and decide who owns the offcut
Weight from the drawing
| Material | Density (kg/m³) | 1 m² at 1 mm weighs | Zorocut uses |
|---|---|---|---|
| Steel (mild; galvanised on its steel base) | 7850 | 7.85 kg | 7850 |
| Stainless steel | 7480–8000 | 7.5–8.0 kg | 7900 (304) |
| Aluminium | 2712; 6061 alloy 2720 | 2.7 kg | 2700 |
| Brass, rolled and drawn | 8430–8730 | 8.4–8.7 kg | 8500 |
| Copper | 8940 | 8.94 kg | 8940 |
Densities are from Engineering ToolBox. A 3000 × 1500 mm sheet of 3 mm steel is 4.5 m² × 3 mm × 7.85 kg = 106 kg; Aston Precision lists that sheet in hot-rolled mild steel at AUD 211.95 before GST, which is AUD 2.00 a kg (computed). In inches the arithmetic is the same: a 48 × 96 in sheet is 48 × 96 ÷ 144 = 32 sq ft, as a PlasmaSpider reply told a shop pricing a job of three such sheets (2021). Keep a date with every price: Eurometal reported north-west European mills' hot-rolled coil at about €750 a tonne in October 2026, against just over €600 a year earlier — a coil price at the mill, not what a stockholder charges for sheet. Zorocut warns when your material price is more than 30 days old.
Three ways to bill the area
An example: ten L-shaped brackets in 3 mm hot-rolled steel, each fitting a 300 × 200 mm rectangle with 350 cm² of metal in it (example), at Aston's price for a 2400 × 1200 mm sheet, AUD 132.00 — AUD 1.95 a kg (computed). Material per part, before markup:
| Billing | Per part in the example | Fair when |
|---|---|---|
| Bounding box + spacing | 303 × 203 mm × 3 mm = 1.45 kg → AUD 2.82 | parts are close to rectangular, or you want one simple rule |
| Share of the nested sheet | 350 cm² × 3 mm ÷ 75 % utilisation = 1.10 kg → AUD 2.14 | repeat work, where the offcut feeds the next job |
| Whole sheets | one 2400 × 1200 sheet ÷ 10 = 6.78 kg → AUD 13.20 | a one-off forces you to buy a sheet whose rest is scrap |
Zorocut bills any of the three. Bounding box adds the part spacing — by default the larger of 3 mm and the thickness — to the part's width and height. The nested share divides the part's net area by the nest's utilisation, and counts a free strip of at least 100 mm that goes back on the rack as not used, so the customer does not pay for metal you keep; before you nest, it assumes 75 % (our estimate). Whole sheets bills every sheet the nest uses, a remnant at its own size. The default markup is 25 %. The online nester shows the sheets and the utilisation behind the number — see sheet utilisation.
Markup: what shops add
- +25–35 % on cost, and a 200 % markup on smaller jobs (Shane Warnick, PlasmaSpider, 2015).
- 1.5 or 2 × material cost, plus the per-inch price and pierces (djreiswig, PlasmaSpider, 2020); “I factor in my material 2 fold”, so that a spoiled cut is not at the shop's expense (TJS, PlasmaSpider, 2022).
- Cost plus at least 30 %, down from 50 % (rodw, LinuxCNC forum, 2018); cost plus 15–30 % from a shop that buys in volume (rikduk, PlasmaSpider, 2014).
- Lapas: 25–30 % is the standard fab-shop markup, 14–16 % on high-volume commodity sheet, 50–100 % on small batches that force a full sheet.
- Aston Precision bills whole sheets at cost, with no markup.
Sources
- Engineering ToolBox, Metals and alloys densities
- Aston Precision, Laser Cutting Cost Estimator (feed, pierce and rate tables)
- Eurometal, European coil mills signal annual contract hikes (2026-10-21)
- Lapas, How to price a laser cutting job (2026-06-01)
- PlasmaSpider forum, What would you have charged? (2015–2016)
- PlasmaSpider forum, CNC Plasma Cutting Excel Pricing Worksheet (2020–2021)
- PlasmaSpider forum, SheetCam – Pricing per inch (2022-09)
- LinuxCNC forum, Calculate plasma cost (2018)
- PlasmaSpider forum, job breakdown and pierce charges (rikduk, Shane Warnick, 2014)
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