Curtain Panel Calculator

Curtain length depends on where you mount the rod and your desired style. Measure from the rod position down to the sill, floor, or desired endpoint. Add your header allowance (for the top fold) and bottom hem allowance to get the total cut length. This calculator does all of that automatically once you enter your window height, rod height above the window, and chosen hem allowances.

Start with the total width of your window, then multiply by a fullness factor based on your style: 2× for standard fullness, 2.5× for a deluxe gathered look, or 3× for sheer panels. Divide that total by the number of panels to find the finished width per panel. The calculator handles all of this and also adds seam allowances to give you a cut-ready width.

For a 60-inch window with standard 2× fullness, you need 120 inches of total curtain width. Split across two panels, each finished panel should be 60 inches wide. For a more luxurious look using 2.5× fullness, aim for 150 inches total — 75 inches per panel. Enter your window width into the calculator to get the exact numbers including hem allowances.

The general rule is that curtains should be 2 to 3 times the width of the window to achieve a full, gathered appearance. A minimum of 1.5× is sometimes used for flat panel styles, while sheers often use 3×. Going below 1.5× results in curtains that look flat and skimpy when closed.

Hanging the rod 4–6 inches above the window frame is the standard recommendation. For a taller, more dramatic look — or to make ceilings appear higher — mount the rod 8–12 inches above the window or even close to the ceiling. This calculator lets you enter any rod height so your curtain length reflects your exact setup.

Common ready-made curtain lengths are 63", 84", 96", 108", and 120". Sill-length curtains typically fall right at or just below the windowsill. Floor-length panels should skim the floor with about a half-inch clearance. Puddle or dramatic-length curtains intentionally pool 4–6 inches on the floor for a formal look.

If your curtain is slightly too long, you can let it puddle on the floor for a dramatic effect, or take up the extra length in the bottom hem. If it's significantly too long, rehemming is the best option. This calculator helps you get the right cut length upfront so you avoid costly mistakes before sewing or purchasing.

When using patterned fabric, you must add extra length to each panel so the pattern aligns across all panels. The rule of thumb is to round up each panel's cut length to the next full pattern repeat. Enter the vertical pattern repeat in the calculator and it will automatically adjust your estimated fabric yardage to include this waste.