Curtain Panel Calculator
Flat panels pulled straight across a window look skimpy. This calculator works out how much fabric width you need for proper fullness, and how many ready-made panels that means.
Your results
Worked example
A 180 cm window, standard fullness of 2, and 140 cm panels:
- Fabric needed: 180 × 2 = 360 cm of flat panel width
- Panels: 360 ÷ 140 = 2.57, which rounds up to 3 panels
- Rod: 180 × 1.2 = 216 cm, so the open curtains can stack back past the glass on each side
Panels are usually split evenly on both sides of the rod. With an odd count like 3, many people buy 4 for symmetry and a fuller look.
How this calculator works
Fullness is what creates the folds when curtains are closed: 1.5 times the window width reads as a light gather, 2 times is the standard decorator recommendation, and 2.5 times gives deep, formal folds. The rod guidance adds about 10 percent of width on each side as stack-back room, a common rule of thumb.
Common questions
How long should my curtains be?
Common choices are sill length, just below the sill, or floor length ending about 1 cm above the floor. Measure from the top of the rod to your chosen endpoint, and remember that panel lengths on the package are measured flat, including the header.
Do blackout curtains need more fullness?
Blackout panels block light best with standard 2 times fullness and a rod that returns to the wall or extends well past the frame, so light cannot leak around the edges. A wrap-around or return rod helps more than extra panels do.
Estimates only. Results are provided for planning purposes and are based on the figures and assumptions shown on this page. Panel widths and shrinkage vary by product; check the package measurements before buying. Mississippi Maple accepts no liability for purchase decisions made using this calculator.