Some standard curtain panel sizes are 63 inches, 84 inches, 95 inches and 120 inches in length. When choosing curtain panels, another important factor to consider is the window's width. The width determines the number of panels needed for covering the window.
Although these are some of the typical panel sizes, the range for ready-made panels can be between 63 and 144 inches. A panel that is 63 inches long typically reaches the bottom of the window sill, and the 95-inch length is suitable for a high window and reaches the floor.
The number of curtain panels required for a window depends on its width. A window that measures up to 36 inches in width requires two panels, and a bigger window that is 112 inches in width requires five to six panels.