Cut List Optimizer
A 96-inch board gives seven 12-inch pieces, not eight. On thin strips the blade costs several — 144 inches into 2-inch pieces loses five.
A 96-inch board gives seven 12-inch pieces, not eight
Every cut but the last turns a blade's width of wood into sawdust, so the count is not stock ÷ piece. It is
⌊(stock + kerf) ÷ (piece + kerf)⌋
Eight twelve-inch pieces need 96 inches of wood plus seven kerfs — 96.875 — and the board is 96. Across 925 realistic stock-and-piece combinations at a ⅛-inch kerf, 12.8% lose a whole piece to the blade. About one in eight.
| Stock | Piece | You'd expect | You get | Sawdust |
|---|---|---|---|---|
| 96″ | 12″ | 8 | 7 | 1.00″ |
| 96″ | 6″ | 16 | 15 | 2.00″ |
| 96″ | 4″ | 24 | 23 | 3.00″ |
| 96″ | 3″ | 32 | 30 | 4.00″ |
| 96″ | 2″ | 48 | 45 | 6.00″ |
| 144″ | 2″ | 72 | 67 | 9.00″ |
On thin strips it costs several
This is the part that surprised me. Total sawdust is the number of cuts times the kerf, so it grows with the piece count while each piece stays small. Ripping a 144-inch board into 2-inch strips should give 72 and gives 67 — five pieces lost to nine inches of sawdust, which is four and a half strips' worth of wood. Across the same sweep, 2.2% of combinations lose two or more. If you are cutting a lot of small parts, the blade is taking a serious share of the board and it is worth buying for it.
Notes
- This packing is good, not optimal. It uses first-fit decreasing, the standard heuristic — an exact answer to a cutting-stock problem is NP-hard and not worth the wait for a workshop cut list. It will occasionally use one stick more than a perfect solution would.
- Measure your actual kerf. A thin-kerf blade is about 3⁄32″, a full-kerf table saw blade ⅛″, and a bandsaw far less. Cut a piece, measure the offcut, and use the real number rather than the nominal one.
- Leave margin for squaring the ends. Rough stock needs an inch or two off the end before any of this arithmetic applies, and boards are rarely the length on the label.
- Cut the longest pieces first. That is what the plan below does, and it is why: a long piece that will not fit anywhere is much worse than a short one, so place the awkward ones while there is still room.
How to use
- Type the cut list as "4 @ 24" for four 24-inch pieces.
- Set the stock length and your actual measured kerf.
- Read the plan — longest pieces are placed first on purpose.
- Add margin for squaring the ends before any of this applies.
Frequently asked questions
How many pieces can I get from a board?
Not stock divided by piece. Every cut but the last turns a blade's width into sawdust, so it is ⌊(stock + kerf) ÷ (piece + kerf)⌋. A 96-inch board gives seven 12-inch pieces, not eight — eight would need 96.875 inches.
How often does the kerf actually cost me a piece?
About one time in eight. Across 925 realistic stock-and-piece combinations at an eighth-inch kerf, 12.8% yield one piece fewer than the naive division suggests. It feels more frequent because the common cases — 96 into 12, 96 into 24 — happen to be among them.
Can the kerf cost more than one piece?
Yes, on small pieces, and it surprised me. Total sawdust is the number of cuts times the kerf, so it grows with the piece count while each piece stays small. Ripping 144 inches into 2-inch strips should give 72 and gives 67 — five pieces lost to nine inches of sawdust. Around 2.2% of combinations lose two or more.
What kerf should I use?
Your measured one. A thin-kerf blade is about 3⁄32 of an inch, a full-kerf table saw blade an eighth, and a bandsaw considerably less. Cut a test piece and measure, because the nominal figure on the blade is not always what it removes.
Is this the optimal cutting plan?
No — it is first-fit decreasing, the standard heuristic. An exact answer to a cutting-stock problem is NP-hard and not worth the wait for a workshop cut list, so this will occasionally use one length of stock more than a perfect solution would.
Why does it cut the longest pieces first?
Because a long piece that will not fit anywhere is much worse than a short one. Placing the awkward pieces while there is still room, then filling the gaps with short ones, is what makes the heuristic work as well as it does.
Should I add margin to the stock length?
Yes. Rough stock needs an inch or two off the end before any of this arithmetic applies, and boards are rarely exactly the length on the label. Measure what you actually have and enter that.
What does the efficiency figure mean?
The share of the wood you buy that ends up in the project, as opposed to sawdust or offcuts. It is a useful sanity check — a very low figure usually means the piece lengths sit awkwardly against the stock, and a different stock length would fix it.
Does this send anything anywhere?
No. Everything is calculated in your browser and nothing is stored or uploaded.
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