Curtain Rod Length Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: July 27, 2026Why extend the rod past the window frame
- Measure the exact width of the window frame or trim.
- Decide on an extension amount per side, typically 3-6 inches.
- Add the extension to both sides of the window width.
- Mount rod brackets at this total width, centered on the window.
Worked example
For a 36-inch wide window with 4 inches of extension on each side:
Rod Length = 36 + (2 x 4) = 44 in
Extending curtain rods beyond the window frame serves two purposes: when curtains are open, they stack against the wall rather than covering part of the glass, and the wider rod visually makes the window (and often the whole room) appear larger than its actual dimensions.