Cutting Stock Calculator with Saw Kerf (How Many Pieces per Board)
How many pieces of a given length you get from a board, bar or pipe once the width of the saw cut is counted, how many boards to buy, and the waste.
Results
The dashed line marks the value you entered.
What this tool does
Every cut turns a strip of material into sawdust, so pieces do not add up to the board length: with a 3 mm kerf, five 450 mm pieces need 2250 + 4 × 3 = 2262 mm, not 2250. The count per board is ⌊(L + kerf) ÷ (piece + kerf)⌋, because only the cuts between pieces cost a kerf — the last piece needs none. The chart shows the catch of cutting to length: waste jumps up and down as the piece length changes, so shaving a few millimetres off a piece can fit one more from each board. Plan with the real stock length, not the nominal one, and leave extra for trimming ends.
Formula
pieces per board = ⌊(L + kerf) ÷ (piece + kerf)⌋ · boards = ⌈pieces needed ÷ pieces per board⌉
Variables
| Symbol | Meaning | Unit |
|---|---|---|
sl | Length of the board or bar you cut from | mm |
pl | Length of each piece | mm |
kf | Saw kerf (width of the cut) | mm |
n | Pieces you need | — |
PC | Pieces from each board | — |
ST | Boards to buy | — |
OF | Offcut left on each full board | mm |
WS | Waste over the whole job (offcuts and kerfs) | % |
Worked example
- Length of the board or bar you cut from2400 mm
- Length of each piece450 mm
- Saw kerf (width of the cut)3 mm
- Pieces you need20
- Pieces from each board5
- Boards to buy4
- Offcut left on each full board138.0 mm
- Waste over the whole job (offcuts and kerfs)6.3 %
Limitations
- Always order a little more material than the calculated quantity. Cuts, breakage and pattern matching create waste that depends on the shape of the job.
- Mixing units is the most common source of error. Convert every input to the units shown next to each field before calculating.