Calculator
Formula used
This tool provides a planning estimate based on a common lift-cord routing model.
+ Control drop + Stack allowance + Return allowance + Safety extra + Hardware extra
- Lift ratio models cord travel through rings and lift path.
- Routing factor adds extra travel across the headrail.
- Allowances cover knots, re-threading, and hardware changes.
How to use this calculator
- Select the unit you use for measuring your shade.
- Enter shade width and height from your finished measurements.
- Pick a routing option based on where the control sits.
- Set lift ratio, then add allowances for your build style.
- Use Auto cords for a quick estimate, or set Manual.
- Press Calculate and download CSV or PDF when needed.
Example data table
These sample values show typical planning inputs and outputs.
| Width | Height | Lift ratio | Routing | Control drop | Lift cords | Total cord (ft) |
|---|---|---|---|---|---|---|
| 36 in | 60 in | 2.00 | Full width | 24 in | 3 (Auto) | ~ 41.0 |
| 24 in | 48 in | 2.00 | Half width | 20 in | 2 (Auto) | ~ 21.8 |
| 60 in | 72 in | 2.20 | Full width | 30 in | 4 (Auto) | ~ 79.0 |
Accurate cord planning basics
Roman shades rely on lift cords to raise and stack fabric evenly. A cord estimate prevents shortages and reduces splices that can slip or create uneven folds. This calculator converts shade dimensions into a planning length that accounts for lift distance, routing style, and control drop. It is useful for new builds, re‑cording, and retrofits where existing cord paths are unknown.
Key inputs that drive length
Height sets the lift travel, while width influences the number of lift cords needed for stable support. As width increases, more cords distribute load and keep battens level. Lift ratio represents how much cord movement is required to raise the shade, reflecting rings, pulleys, and friction. Selecting a routing option helps model whether cords return to one side or travel across the headrail.
Understanding routing and returns
Routing affects both performance and material use. A full‑width route adds extra horizontal distance because cords traverse the headrail before reaching the control side. A split route shortens cross‑travel but may require two pull cords or a different clutch arrangement. The calculator includes a return multiplier to model straight runs or doubled paths used with certain cord locks.
Allowance for installation realities
Real installations need margin. Add allowance for knots, cord ends, tensioning, and trimming after final leveling. Fabric thickness, ring spacing, and liner weight can increase friction, so a modest safety factor helps avoid a cord that is too short after re‑threading. If you plan to wrap around a cleat or use a longer control drop for accessibility, enter that extra drop directly.
Using results for safer operation
Use the computed total to buy cord in practical increments and to plan cutting lengths per lift cord. Document your settings so future maintenance matches the original geometry. After installation, cycle the shade repeatedly, check that folds stack evenly, and confirm that cords track without rubbing sharp edges. A careful estimate supports smoother operation and longer hardware life. for years.
FAQs
1. What is lift ratio, and how do I choose it?
Lift ratio estimates how much cord movement is needed per unit of shade lift. Many simple ring paths are near 2.0. Use 2.2–2.6 for tighter routing, extra pulleys, or heavy liners that increase friction.
2. How many lift cords should a Roman shade use?
Use more cords as width increases to keep folds even. A common guideline is one cord every 8–12 inches of width, with a minimum of two. The calculator can auto-suggest a count based on your width.
3. Should I add extra length beyond the calculated total?
Yes. Add allowance for knots, cord locks, trimming, and final leveling. A 5–10% safety margin is typical. If you need a longer control drop for reach, include it directly in the control drop field.
4. What routing option should I pick for my headrail?
Choose full-width if cords travel across the headrail to a single control side. Choose split if cords exit closer to their lift points or if you plan dual pulls. When unsure, full-width is a safer estimate.
5. Does fabric type change the cord length result?
The geometric length stays similar, but heavier fabric and liners increase friction and may require more safety margin. Thicker stacks can also demand slightly higher lift ratio. Use a small extra percentage if the shade feels resistant.
6. Can I use this for re-cording an existing shade?
Yes. Measure the finished shade and match the routing style you see inside the headrail. If the original path is unclear, estimate with full-width routing and add margin, then verify by dry-threading before cutting all cords.