Evidence hierarchy
We prefer manufacturer manuals and product specifications, then established workroom and fabric-supplier guidance, then current major-retailer dimensions. Proprietary heading systems use their manufacturer documentation.
- Cross-check important ratios and dimensions across more than one relevant source.
- Record disagreements and retain ranges.
- Keep a reviewed date with every structured record.
- Use current product pages only as examples of commercial availability.
Calculations
Pure mathematical steps—unit conversion, multiplication by fullness, division across panels, rounding a cut to a whole repeat—are separated from the design assumptions entered by the user. Calculator defaults remain editable.
Editorial scope
Each guide is published only when its calculation, assumptions, source notes, and limitations are complete. Closely related questions are handled together on one useful page instead of being split across repetitive pages.
Corrections
When a source changes, the relevant calculations and pages are reviewed together. We record the reason for each correction so related guidance can be checked consistently.