Material consumption including waste
How many boards should you order, and how many litres of paint are needed? Enter the area and the unit size or coverage, and add waste.
Your numbers
Offcuts, leftovers and miscuts. Use your trade's own experience.
More options: Packs, Price
It's on the pack. 0 = you buy loose pieces.
Your own price. It is included if you save to a job.
Answer
Number of units
10pcs.
Area including waste
26.4m²
Area you buy
28.8m²
How to work it out
- 1With waste: 24 m² · (1 + 10 / 100) = 26.4 m²Add the waste to the area BEFORE you divide — offcuts and miscuts need a sheet too.
- 2One unit: 2,400 mm · 1,200 mm = 2.4 m · 1.2 m = 2.88 m²Measurements in mm are divided by 1,000 to become metres, so both areas are in m².
- 326.4 / 2.88 = 9.17 → 10Always round UP — you cannot buy half a board.
The formula
number = area · (1 + waste/100) / area of one unit
Always round UP — you cannot buy half a board.
litres = area · coats / coverage · (1 + waste/100)
The coverage is how many m² one litre covers in one coat.
area = Σ (+ surfaces) − Σ (windows, doors)
A composite surface: add the parts together and subtract the openings.
walls = 2 · (l + w) · h − openings
The room's perimeter times the height gives all four walls at once.
number = length / spacing (rounded up) + 1
+1 because there is a piece at both ends — one more piece than there are gaps.
packs = number / pieces per pack (rounded up)
The remainder is the pieces left over in the last pack.
Waste, coverage, c/c spacing and pack size depend on the material and the job — use the figures from the product, the drawing and your trade.
In depth: more numbers and “what if”
What if the waste is different?
| Waste | Area including waste | Number of units |
|---|---|---|
| 0 % | 24 m² | 9 pcs. |
| 5 % | 25.2 m² | 9 pcs. |
| 10 % | 26.4 m² | 10 pcs. |
| 15 % | 27.6 m² | 10 pcs. |
| 20 % | 28.8 m² | 10 pcs. |
More: Workshop maths
- Slope and fallFall from level to level, in per cent, per mille, degrees and mm per metre — and the height difference.
- Mix ratio1 : 50, three parts, percent, dilution and the cross rule — how much of each.
- Density and weightThe weight of plates, bars and pipes — per piece, per running metre and in total.
- Unit priceCompare offers on price per kg, litre, metre or piece.