Linear length is not a shopping list
Three rectangular frames each need two horizontal pieces and two vertical pieces. Adding their lengths gives the finished perimeter, but it does not tell you how many stock lengths to buy. A 190 cm piece will not fit into a 180 cm length, even if the total material area or length seems sufficient. The arrangement of cuts matters.
Know which edge your measurement describes
Our frame dimensions are the outside, long-point dimensions for a rectangular frame with 45-degree corners. They are not inside openings or centreline lengths. The cut planner first creates square blanks slightly longer than those finished lengths. The mitres are then cut within each blank. The blank allowance is editable because the required extra depends on your equipment and process. This is a quantity plan, not a sawing tutorial.
Keep three allowances separate
Kerf is the width lost to a cut. End trim is the material discarded from each end of a stock length. Blank allowance is added at each end of every finished piece. For a 76.67 cm finished piece with 0.5 cm at each end, the square blank is 77.67 cm. With a 0.3 cm kerf, the planner reserves 77.97 cm of usable stock for it. Reserving one kerf per blank is intentionally conservative, including the last blank in a length.
How the packing estimate works
The planner sorts the blanks from longest to shortest and places each in the first stock length with enough remaining space. If none fits, it opens a new stock length. This method is called first-fit decreasing. It provides a reproducible cutting arrangement, but it is not guaranteed to find the mathematical minimum. Review the diagram and any usable offcuts before ordering. A shorter listed offcut cannot be assumed to replace a full-length piece.
Allow for the real material
Knots, damage, finish matching and mistakes are not predicted. The reported stock quantity is the quantity for the displayed cutting arrangement, with the allowances you entered. It does not include an automatic percentage for defects. Choose any additional spare material separately. Recheck actual stock dimensions, the available lengths and the physical wall before buying or cutting. If a piece is too long, the tool asks for longer stock rather than silently assuming a joint.