The calculation almost everyone starts with is simple: add up the area of the parts, divide by the area of one board and round up. Sometimes it works. Other times you get to the saw one board short, because the parts do not fit on the board the way they add up on paper. In this guide you will see why that happens, what uses up the board apart from the parts, and how to arrive at a chipboard requirement you can rely on.
Why the area calculation comes out too low
The net area of the parts tells you how much chipboard ends up in the furniture, not how much chipboard you use. Between the two values sit a few things that simple division does not see:
- Saw kerf. Every cut turns a few millimetres of board into sawdust.
- Trimming. The factory edges are cut off, so the usable area is smaller than the one on the board's label.
- Grain. Parts with fixed grain cannot be rotated, so they do not fill every free space.
- Geometry. Sometimes the area would be enough but the shapes do not fit: strips are left that are too narrow for any part.
- Different materials. The carcass, the fronts and the back are different boards. You cannot add their areas together.
That is why the area calculation is fine as a first estimate, but the buying decision should be based on how the parts are actually laid out on the board, in other words on a cutting plan.
What uses up the board apart from the parts
Saw kerf
On panel saws and sliding table saws, the cut width is usually between 3 and 4.5 mm. It seems small, but on a board with 20–30 cuts it adds up. More importantly, the kerf decides whether two parts fit side by side: two 1024 mm parts do not fit on a usable width of 2050 mm, even though 2 × 1024 = 2048. You will find the details in the article on saw kerf and board trimming.
Board trimming
The edges of a raw board are often chipped in transport or not perfectly straight. Typical trimming is 10–15 mm on each factory edge. A 2800 × 2070 mm board trimmed by 10 mm on all 4 sides has a usable area of 2780 × 2050 mm, that is 5.70 m² instead of 5.80 m².
Grain
Cabinet side panels, doors and drawer fronts usually have the grain running in a specific direction. That means you cannot turn them by 90° just to fill a gap. The more fixed-grain parts you have, the higher the consumption. See also the guide to chipboard grain direction when cutting.
Offcuts
Every cutting plan leaves offcuts. Some are waste, others are reusable offcuts, large enough for a future order. A good offcut is not a loss, but you still pay for the whole board when you buy it. Read about reducing waste in the article on chipboard cutting waste.
Worked example: a 600 mm base cabinet
Take an ordinary kitchen cabinet: 600 mm wide, 720 mm carcass height, 560 mm deep, in 18 mm chipboard. Full-height side panels, the bottom between the sides, two top rails, one shelf, a 3 mm HDF back and two doors in a different decor. The inside width is 600 − 2 × 18 = 564 mm.
| Part | Size (mm) | Qty | Material | Area (m²) |
|---|---|---|---|---|
| Side panel | 720 × 560 | 2 | White chipboard 18 mm | 0.8064 |
| Bottom | 564 × 560 | 1 | White chipboard 18 mm | 0.3158 |
| Rail | 564 × 100 | 2 | White chipboard 18 mm | 0.1128 |
| Shelf | 564 × 500 | 1 | White chipboard 18 mm | 0.2820 |
| Back | 716 × 596 | 1 | HDF 3 mm | 0.4267 |
| Door | 716 × 297 | 2 | Decor chipboard 18 mm | 0.4253 |
| Total | 9 | 2.3691 |
The requirement for a single cabinet
Area of a 2800 × 2070 mm board: 2.8 × 2.07 = 5.796 m².
The “total area” calculation: 2.3691 / 5.796 = 0.41 boards. It looks like half a board is enough.
By material: white chipboard 1.5170 m², decor chipboard 0.4253 m², HDF 0.4267 m².
In reality you need three different boards, one of each material, or suitable offcuts from stock. A part can only be cut from its own material.
Five cabinets: area vs. the real layout
Now make five identical cabinets and look only at the white chipboard for the carcasses. The list multiplies: 10 side panels, 5 bottoms, 10 rails and 5 shelves, 30 parts in total.
White chipboard for 5 cabinets of 600 mm
Net area: 5 × 1.5170 = 7.585 m².
By area: 7.585 / 5.796 = 1.31 boards, so 2 boards.
With a 30% margin: 7.585 × 1.3 = 9.861 m², or 1.70 boards, still 2 boards.
Layout on board 1 (2780 × 2050 mm usable after trimming, 4 mm kerf): three 560 mm strips, each with 3 side panels and a bottom (3 × 720 + 564 + 3 × 4 = 2736 mm). That leaves a strip of about 350 mm, which takes all 10 rails, in three rows.
Board 1: 9 side panels, 3 bottoms, 10 rails, that is 5.140 m² used, about 89% of the board.
Board 2: 1 side panel, 2 bottoms, 5 shelves, that is 2.445 m². More than half of the board remains free, as a reusable offcut.
Here the area calculation got the number of boards right. The parts are rectangles that lay out well in strips of the same width. But the second board shows that the real requirement also includes a large offcut, which you pay for now and use later.
If the second line of the calculation gives you 1.1 or 1.2 boards, check whether you can move a few parts onto an offcut from stock. Sometimes you save a whole board.
When the geometry needs an extra board
Kitchen cabinets lay out easily. Long, wide parts, such as wardrobe side panels, are much harder. This is where the area calculation is simply wrong.
Four wardrobe side panels of 2400 × 580 mm
Net area: 4 × 2.4 × 0.58 = 5.568 m², or 0.96 of a 5.796 m² board. By area, a single board.
Across the usable width of 2050 mm, three side panels fit: 3 × 580 + 2 × 4 = 1748 mm. A fourth would need 4 × 580 + 3 × 4 = 2332 mm.
Two do not fit along the length: 2 × 2400 = 4800 mm, far more than 2780 mm. Rotated by 90°, the 2400 mm side does not fit in 2050 mm.
Result: 2 boards, not one. You use only one side panel from the second, and the remaining offcut of about 2780 × 1460 mm goes into stock.
With a 30% margin (5.568 × 1.3 = 7.24 m², or 1.25 boards) you would still have arrived at 2 boards. The margin protects you in most cases, but only the real layout tells you for sure.
How much margin to add for a quick estimate
When the customer expects a price on the spot and you have no time for a full plan, you can work like this:
- 1Split the parts by material
Carcass, fronts, back, shelves in another decor: each material has its own total. Never add HDF to chipboard, or white to decor.
- 2Calculate the net area for each material
Length × width × pieces, using finished sizes. For a quote-level calculation, edge banding does not change the result.
- 3Add a margin for kerf, trimming and gaps
OptimCut uses 30% as the recommended value. For many small parts you can go lower; for large, fixed-grain parts keep the margin or check the geometry.
- 4Check large parts separately
How many long side panels fit across the board width? If the answer is 3 and you have 4, you need one more board, whatever the area says.
- 5Round up and subtract the offcuts
Round up to whole boards, then check which reusable offcuts of the same material you already have in the workshop.
For a quote, this method is enough. For ordering boards and for cutting, make the cutting plan. A panel cutting calculator gives you the exact number in a few minutes.
How OptimCut calculates the requirement and checks the stock
In OptimCut you do not calculate by hand. You describe the furniture once, as a recipe, and for each order the software goes through the steps above for you:
Requirement per material
The Material requirement step shows the number of parts and the net area for each material, plus the recommended value, with 30% extra for the saw blade, trimming and gaps where nothing else fits.
Stock boards
It lists only boards of the right material on which at least one part fits, reusable offcuts included, and proposes the quantity for the requirement + 30% by itself.
Stock warning
If you select less than the 130% recommendation, you get a warning. You can continue, but enough area does not guarantee that every shape fits.
The real plan
The optimization lays out the parts taking the saw kerf, trimming and grain into account. If a part does not fit, the Unplaced parts message appears before you cut anything.
Once you confirm the cutting job, the boards used are taken out of stock, and you add the good offcuts back for the next order. The CSV export gives you the board requirement, the cut list, the edge banding requirement and the offcuts, ready to open in Excel. For a quick estimate, without stock and without recipes, use Quick optimization: enter the board and part sizes and see the plan instantly. Every step is described in the user manual.
Conclusion
Area gives you a first idea, not a number of boards. Calculate per material, take kerf, trimming and grain into account, check large parts separately and add a margin of about 30% for a quick estimate. For the actual order, let a cutting plan tell you exactly how many boards it takes and which offcuts are left.
You can try it on your own cabinets with a free Trial account: 3 optimizations per month, up to 100 parts per optimization, no card. If you cut every day, see the Pro plan as well.
Frequently asked questions
How many chipboard sheets do I need for a 600 mm kitchen cabinet?
The carcass of a 600 mm base cabinet uses about 1.5 m² of chipboard, less than a third of a 2800 × 2070 mm board. But you also need a board or an offcut for the fronts and for the HDF back, because each material is cut separately.
How much margin should I add to the net area of the parts?
For a quick estimate, a margin of about 30% usually covers the saw kerf, trimming and the gaps between parts. It is also the value OptimCut recommends. For large, fixed-grain parts, check separately how many fit across the board width.
Why is the area calculation not enough?
Because the parts have to fit as shapes, not just as area. The saw kerf uses material on every cut, trimming makes the board smaller, and fixed-grain parts cannot be rotated into the gaps that are left.
Does edge banding matter when calculating chipboard requirements?
For a board estimate, hardly at all, because edge banding changes the sizes by a few millimetres. It does matter for the cutting plan: OptimCut subtracts the band thickness from the finished size and adds the pre-milling, so the part comes out at exactly the right size.
Can I use offcuts from stock when calculating the requirement?
Yes. In OptimCut, reusable offcuts are kept in the same stock as new boards and appear in the board selection for the matching material. If some parts fit on offcuts, you need fewer new boards.
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