Cutting plan
How many bars you really need, where to cut and what is left over
Use the same unit in every field. The end trim is the damaged or bent bit you cut off each bar before you start, leave 0 if you do not need it.
Write the length first and the quantity second, for example 900 x 3. You can put a name in front if it helps, for example legs 900 x 3. Lines starting with # are ignored.
How to write the piece list
One line per size, length first and quantity second, for example 900 x 3. Instead of the x you can use a space, an asterisk or an at sign. You may put a name in front (legs 900 x 3) and it comes back on the pattern, so you know which piece you are cutting. Decimals accept both the comma and the dot, and lines starting with # are your own notes. If a line is unclear the tool stops and tells you which one, instead of guessing for you.
How the plan is worked out
This is the one dimensional cutting stock problem and it has no formula, only trial. The tool starts from the longest piece and drops it into the first bar with room (first fit decreasing), then repeats looking for the tightest fit, then runs the filling hundreds of times with the list shuffled, and finally tries to empty the least loaded bar by moving its pieces elsewhere. The plan with fewest bars wins; on a tie the one leaving the longest single offcut wins, because one long piece can be reused and ten stubs cannot. The random generator uses a fixed seed, so the same list always gives the same plan.
The blade eats more than you think
Every pass of the blade removes its own thickness, the kerf: around 3 mm for a circular saw, 1 mm for a hand saw, close to zero for shears. Between two neighbouring pieces the blade passes once only, so n pieces on a bar mean n-1 inner passes plus one to free the offcut. It sounds small, but forty cuts of 3 mm add up to 12 cm, a whole piece you had not planned for. That is why the kerf sits inside every fit here, instead of being added at the end.
How to read the waste figure
Waste is the difference between the material you buy and the material that ends up in the finished pieces, and it covers blade, offcuts and end trim. The panel breaks it down line by line and the figures always add up. Below it you also get the waste really lost, worked out by setting aside the offcuts at least as long as your shortest piece: the ones that, once stored, will still be good for something.
Declared limits
The calculation works in one dimension, so it fits bars, battens, tubes, profiles, skirting and planks, but not sheet or panel cutting, which is a very different two dimensional problem. Every bar is treated as identical and flawless, grain direction and knots to avoid are not considered, and the answer is the best of the plans tried, not a proven optimum: when the plan does reach the theoretical minimum computed from the material, the page says so. Everything runs inside your browser and no data is sent anywhere.