How to use the cut list optimizer
- Enter the board lengths you can buy. List what your yard stocks, like
8', 10', 12', 16'. To plan around one length, say a lift of 16s, enter just that one. - Set the kerf. The kerf is the wood the blade turns into sawdust. A standard 7-1/4" framing blade is about 1/8". Thin-kerf blades are closer to 3/32".
- Type your cut list, one length per line, as quantity @ length:
6 @ 34 1/2. Feet and inches work too:2 @ 3' 6. - Read the plan. "Boards to buy" is your shopping list. The cutting plan shows which cuts come out of each board, and the bars draw it to scale.
How it finds the fewest boards
This is the classic "cutting stock" problem. The calculator fills one board at a time. For each board it checks every stock length you entered and finds the combination of remaining cuts that leaves the smallest offcut on that board. It keeps the length that fills best, and when everything left fits on one board, it picks the shortest board that holds it all. It runs that again for each single stock length and shows the plan that buys the least total lumber.
Each cut uses its length plus one kerf. The last cut on a board doesn't need a kerf if it lands exactly at the end, so a board fits cuts whose lengths plus kerfs come to no more than the board length plus one kerf.
Example: four 92-5/8" studs. Two of them plus two kerfs take 92-5/8 + 92-5/8 + 1/8 + 1/8 = 185-1/2", so two fit on a 16' (192") board with 6-1/2" left. Two 16s or four 8s waste the same wood, so the plan picks two 16s: fewer boards to carry and handle.
Why kerf matters: a 60" and a 36" cut add up to exactly 96", but with a 1/8" kerf they don't come out of an 8' board: 60 + 1/8 + 36 = 96-1/8". Set the kerf to 0 and the calculator will put them on one board. In real life you'd end up 1/8" short.
Tips for less waste
- Cut the longest pieces first, then fill the offcuts with short pieces like blocking and cripples.
- Check real board lengths. Most framing lumber runs a little long (an "8-footer" is often 96-1/4" or more). That's your safety margin for squaring the ends. If the ends are split or out of square, use the trim field.
- Mark offcuts you'll reuse. An 18" offcut is a block later. Keep a pile near the saw.
- Group by size. Run the optimizer once per lumber size (all the 2×4s, then all the 2×6s). It doesn't mix sizes.
FAQ
How do I figure out how many boards I need for my cuts?
List every cut and its quantity, add one saw kerf (about 1/8") per cut, and fit the cuts onto the board lengths you can buy, longest cuts first. This calculator does that fitting for you and shows which cuts come from each board.
What is saw kerf and why does it matter?
Kerf is the width of wood the saw blade removes, about 1/8" for a standard circular saw blade. Every cut costs one kerf, so two pieces that add up to exactly the board length won't both fit. Over many cuts, kerf adds up.
Is it cheaper to buy long boards or short boards?
Long boards often cost a little more per foot, but they let you fit more combinations of cuts with less waste. Enter the lengths your yard sells and compare the plans. Use the lumber cost calculator to price them.
Does the optimizer always find the best possible plan?
It finds the best fill for each board and tries several strategies, which gives the best plan or one very close to it for real cut lists. Cutting-stock problems are hard to solve perfectly, so a hand-made plan may sometimes save a board on very long lists.