By Zencalcy Editorial TeamLast reviewed About us
Proper curtain sizing depends on window dimensions, mounting height, and desired fullness. Rods mount 4 to 6 inches above the frame and extend 3 to 6 inches each side, and the panel width multiplies that opening by a fullness factor so the fabric gathers instead of hanging flat.
Curtain length, width and fullness for windows.
Curtain width = window width × fullness Curtain length = window height + mounting height
Fullness is typically 1.5× to 3× the window width for a gathered look — pinch-pleat headings want 2 to 2.5×, ripple-fold 2 to 2.5×, and tab-top or rod-pocket styles only 1.5 to 2×.
| Symbol | Meaning |
|---|---|
| windowW | Window width (in ft). |
| windowH | Window height (in ft). |
| mountH | Mounting height above window (in ft). |
| fullness | Fullness multiplier (1.5-3×). |
Curtain width = 3 × 2 = 6 ft; Curtain length = 4 + 1 = 5 ft.
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For 2× fullness, curtains should be 6 ft wide (3 ft per panel, 2 panels). Mount the rod 3 to 6 inches beyond each side of the frame so the open panels clear the glass.
Results use standard construction estimating arithmetic: volumes from measured area and depth, unit weights from published material densities, and code-referenced spans or clearances where the page names a code. Quantities are rounded up to whole saleable units and include the stated waste allowance. These tools are planning aids, not structural design, and do not replace a licensed engineer, a local code check, or a contractor's site measurement.
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Content updated: September 2026