Begin with prepared fabric dimensions
Measure fabric in the condition in which you will cut it. If you prewash, dry and press it first, use the resulting width rather than assuming that the nominal width on the label remains available. The workbench takes one common width for fabrics A, B and C. When the widths differ, using the narrowest measured width is a conservative way to keep all three plans within their available cloth.
Subtract the selected selvedge exclusion from both sides. The remaining width is the space available for cross-cuts. Set a square-up allowance at each end so the first usable strip does not depend on an uneven cut edge. These losses appear separately from the extra percentage reserve; they are not hidden inside a single unexplained yardage multiplier.
Read the relationship between patches and strips
Each patch starts with a finished rectangle defined by the square block and its equal-cell matrix. A seam allowance is added to all four edges. The cut width is the finished width plus two seams, and the cut height follows the same rule. Pieces are grouped into strips of equal cut height and placed left to right without rotating them.
The cutting map gives each strip an identifier and each cross-cut a position. Its vertical direction follows lengthwise grain. After a strip is cut across the usable width, cross-cut the listed rectangles in order. Gray space at the end of a strip is unused cloth, not an additional patch. Keep patch IDs with your pieces so the block assembly list refers to the actual cuts you made.
Understand the purchase calculation and exclusions
The required cut length is the sum of strip heights plus the two end allowances. The planner then adds your percentage reserve and rounds the purchase upward to the selected increment: one eighth of a yard or one tenth of a metre. The display shows both the construction length and the rounded purchase so you can see how the estimate was formed.
This is a valid constructive plan, not a claim that no alternative layout could use less cloth. Backing, batting, binding, borders and later quilting contraction are outside this top-only calculation. A reserve is useful for handling mistakes, but it does not measure fabric shrinkage or guarantee enough extra for motif matching. Check the design and sew a sample block before buying an entire project’s materials.