Calculator Inputs
Example Data Table
| Shade width | Shade drop | Cords | Vertical spacing | Rows | Total rings |
|---|---|---|---|---|---|
| 36 in | 54 in | 3 | 8 in | 6 | 18 |
| 48 in | 72 in | 4 | 7 in | 9 | 36 |
| 60 in | 84 in | 5 | 8 in | 10 | 50 |
Examples assume 6 in top and bottom clearances with fixed spacing.
Formula Used
- Usable drop =
drop − top_clearance − bottom_clearance - Ring rows =
floor(usable_drop ÷ vertical_spacing) + 1(minimum 2 rows) - Base rings =
rows × cords - Total rings =
base_rings + (extra_per_cord × cords) + extra_total - Even distribution mode sets
actual_spacing = usable_drop ÷ (rows − 1)
How to Use This Calculator
- Measure the finished shade width and drop in one unit.
- Choose cord mode: manual cords, or auto by target spacing.
- Set ring vertical spacing and clearances for top and hem.
- Use even spacing when you want perfectly distributed rows.
- Press calculate, then export CSV or PDF for your workbench.
Ring Planning for Consistent Lifts
Ring placement drives how evenly a roman shade lifts and stacks. A predictable grid reduces diagonal pulls, limits fabric twist, and makes cord tension easier to balance. This calculator turns your width, drop, and spacing targets into a repeatable ring plan. The output includes ring rows, estimated cord spacing, and a position map you can print at the workbench. For outdoor-adjacent windows, use UV-stable thread and corrosion-resistant rings to maintain performance across seasonal temperature swings daily.
Spacing Data That Fits Real Fabric
Vertical spacing is most commonly set between 6 and 10 inches (or the metric equivalent), depending on fabric weight and the crispness you want in each fold. Smaller spacing yields more folds and more rings, improving control but adding sewing time. Larger spacing reduces hardware and labor, but can create a softer, less structured stack on tall shades.
Cord Count, Width, and Side Margins
Wider shades generally benefit from additional lift cords to distribute load and keep the bottom bar level. The auto mode estimates cord count from a target cord spacing, then clamps the result to a practical range. Side margins keep cords away from seams and edge stress, which is especially helpful in humid garden rooms where fabrics can relax over time.
Clearances and Usable Drop
Top and bottom clearances reserve space for the headrail, mounting hardware, and hem. The calculator removes these clearances to compute usable drop, then converts that length into ring rows. Even distribution mode keeps the first and last rows aligned to your clearances while smoothing the spacing between them for a clean pattern.
Exports for Cutting Lists and QA Checks
The CSV export provides a full ring position map with row and cord indices plus X/Y coordinates, which helps with marking tape and quality checks. The PDF report summarizes totals and key settings for quick review. Add extra rings as a small buffer for repairs or revisions when working around potting benches, greenhouse glazing, or frequent moisture.
FAQs
How many cords should a roman shade use?
Most shades use 2–5 cords. Wider shades usually need more cords to keep the bottom bar level and reduce diagonal pull.
What vertical spacing is typical for ring rows?
A common range is 6–10 inches. Smaller spacing increases control and fold definition, while larger spacing reduces sewing time and hardware.
What does “even distribution” change?
It keeps your chosen top and bottom clearances, then spreads ring rows evenly between them. This is useful when you want a perfectly uniform pattern.
Why set side margins for cords?
Side margins keep cords off seams and edge stitching. This reduces wear and helps the shade lift smoothly, especially where humidity can soften fabrics.
Do I need extra rings?
A small buffer is smart. Extra rings cover mistakes, repairs, or later adjustments, and they are inexpensive compared with re-opening finished seams.
How do I use the position map?
Mark each row line from the bottom clearance upward, then place rings at the listed X positions. The CSV is best for full maps; the on-page preview is a quick check.