What the Curtain Rod Length Calculator actually calculates
Rod length is window width plus two equal side extensions. Overall width adds two equal finial allowances. The engine does not estimate stack-back from fabric weight or fullness and does not choose bracket spacing, support count, or a load-rated rod.
The calculation path
Window width receives an extension on both sides based on panel weight and desired stack-back.
Inputs that can change the answer
- Window width: Enter window width in m.
- Extension each side: Enter extension each side in m.
- Finial allowance each side: Enter finial allowance each side in m.
Checks that stay outside the formula
Check for adjacent walls, cabinets, and switches before extending the rod.
A practical order for entering the data
- Measure the window width in metres.
- Choose the rod extension on each side after considering curtain stack-back and nearby obstructions.
- Enter each finial's additional projection and compare both rod-only and overall widths with the available wall.
Project walkthrough: Curtains: from window measurement to fabric order
Project walkthrough: Compare blinds and curtains from the same window measurements
Engine check using the prefilled sample
Window-treatment example: window width = 1.6 m, extension each side = 0.2 m and finial allowance each side = 0.08 m. Replace the sample opening and fabric or hardware values with measurements taken for the mounting method you plan to use.
Results for these inputs
- Rod excluding finials
- 2.00 m
- Overall width
- 2.16 m