Calculator
Choose units, set allowances, then calculate.
Example data table
Use these as a starting point and adjust for your space.
| Opening | Mount | Extension each | Overlap | Return each | Ends | Rod length (rounded) |
|---|---|---|---|---|---|---|
| 60 in | Outside | 6 in | 2 in | 0 in | Yes (1 in) | 76.25 in |
| 120 in | Outside | 8 in | 3 in | 3 in | Yes (1.5 in) | 147.5 in |
| 150 cm | Inside | 0 cm | 0 cm | 0 cm | No | 150.0 cm |
Examples are illustrative. Hardware styles vary, so confirm against your specific rod and brackets.
Saved results (latest 25)
Exports use this saved table.
No saved results yet. Run a calculation to store history.
Formula used
The calculator sizes the rod using your allowances.
Base span is the opening width. For inside mounting, the calculator subtracts the inside clearance.
Rod length = Base span + 2×Side extension + Center overlap + 2×Return length + 2×End allowance (optional)
- Side extension gives space for panels to stack past the opening.
- Center overlap helps reduce a center light gap.
- Return length supports wrap-around styles.
- End allowance is added only when ends are included.
- The final value is rounded up to your increment.
How to use this calculator
A quick workflow for clean installations.
- Measure the opening where the curtains will cover.
- Choose mount type and set inside clearance if needed.
- Set side extension based on how far panels should stack.
- Add overlap and returns if you want extra coverage.
- Choose rounding to match common rod sizes.
- Calculate, then export results to keep measurements organized.