The quick answer: add up the area of every piece, divide by the area of one sheet, and add 15 to 20 percent for blade width and waste. Round up to the next whole sheet. That gives a good estimate, but the only way to be sure is to lay the pieces out on a sheet.
Step 1: Find the area of each piece
Multiply length by width for each piece, then multiply by the quantity.
Step 2: Add the areas together
This is the total area of parts you need, before any waste.
Step 3: Divide by the area of one sheet
A standard 244 × 122 cm sheet is 29,768 cm². A 275 × 183 cm sheet is 50,325 cm².
Step 4: Add 15 to 20 percent
Blade width, trim and offcuts that are too small to use all take material. This margin covers them.
Worked example: a small bookcase
Suppose the project needs these pieces, all cut from 244 × 122 cm sheets:
- 4 sides, 180 × 30 cm: 4 × 5,400 = 21,600 cm²
- 2 shelves, 88 × 28 cm: 2 × 2,464 = 4,928 cm²
- 1 top and 1 bottom, 90 × 30 cm: 2 × 2,700 = 5,400 cm²
The total is 21,600 + 4,928 + 5,400 = 31,928 cm².
One sheet is 29,768 cm², so 31,928 ÷ 29,768 = 1.07 sheets. That already means one sheet is not enough.
Adding 15 percent gives 31,928 × 1.15 = 36,717 cm², which is 1.23 sheets. Round up, and the estimate is 2 sheets.
This is only an estimate. Two sheets might not be enough once the blade width is counted for every cut, and a long side may not fit across a sheet at all. Check the layout before you buy.
Check the layout before you buy
The area method can say 2 sheets when the real layout needs 3, or it can say 2 when the pieces fit on 2 with room to spare. Cutly works out the exact layout in your browser: it shows how many sheets you need, how each sheet is cut and how much is left over. Your parts are never uploaded.