Curtains Calculator

8 Tips for Measuring and Ordering Curtains the Right Size

Tip 1: Rod Placement Determines Curtain Length—Measure After Installing the Rod

Don’t order curtains before the rod is installed. Curtain length is measured from the bottom of the rod (or from clips/rings if hanging from the rod), not from the top of the window frame. Install your rod first at the desired height—typically 4-6 inches above the window frame or 8-12 inches for a dramatic, floor-length look. Once the rod is mounted, measure down from the rod to wherever you want the curtain to end (sill, apron, or floor).

Tip 2: Curtain Length Comes in Standard Sizes—Measure to the Nearest Standard

Stock curtains come in set lengths: 63, 84, 95, 108, and 120 inches. Don’t order custom lengths unless necessary. Measure your rod-to-ending-point distance and round to the nearest standard size. If the distance is 70 inches, order 84-inch curtains and hem them to length. If it’s 50 inches, order 63-inch curtains—a 13-inch difference is much cheaper than a custom order.

Tip 3: Calculate Curtain Rod Width Carefully—Panels Should Overlap Slightly

Measure the rod length from end to end. Curtain panels typically come in widths like 50, 52, 54, and 96 inches. You usually want two panels per window, and they should overlap slightly at the center when drawn closed—overlap of 4-6 inches looks professional. If your rod is 60 inches, two 54-inch panels will overlap about 6 inches at center, providing good coverage and light blocking. If you use too-narrow panels, they won’t cover the window when drawn.

Tip 4: Account for Fullness—Curtains Look Better Gathered Than Stretched Flat

Curtain fullness is how much fabric bunches at the rod when curtains are drawn. A fullness of 1.5x to 2x means the total fabric width is 1.5 to 2 times the rod width. A rod that’s 60 inches wide with 2x fullness needs 120 inches of total fabric (two 60-inch panels). Standard curtain panels are sized for 1.5x to 2x fullness, so using two panels per window usually gives the right look without special ordering. Thin, skimpy curtains that stretch flat across the rod look cheap; full, gathered curtains look intentional.

Tip 5: Sheer vs. Blackout Affects How You Measure and Layer

Sheer curtains allow light through and are often used alone or layered under blackout panels. Blackout curtains block most light and are often paired with sheers. If layering, measure the rod twice—two separate rods if you want independent operation, or one rod with both curtains hung from rings/hooks. Sheer panels can be narrower (they’re see-through); blackout panels should be wider for better coverage and light blocking.

Tip 6: Measure Rod Width Multiple Times Across the Window

Some rods sag slightly in the middle or walls aren’t perfectly vertical. Measure at the top, middle, and bottom of the window frame. If measurements vary by more than 0.5 inch, use the widest measurement for ordering—this ensures panels will cover the window even if the rod sags slightly. If the rod is severely sagged (over 1 inch variation), reinforce or replace it before ordering curtains.

Tip 7: Consider How Curtains Will Hang at Corners and Edges

Curtains at the edge of a window should extend at least 2-3 inches past the window frame on each side so light doesn’t leak around the sides when curtains are closed. Measure rod length, then add 4-6 inches total to account for this overhang. A window that’s 36 inches wide with a rod that’s 40-42 inches wide provides this light-blocking overhang on both sides.

Tip 8: Hem Length Affects the Final Look—Decide Before Ordering

Curtains can end at the sill, the apron (just below the window), or the floor. Sill-length takes the least fabric; floor-length takes more and looks more formal. Puddle length (where curtains pool on the floor 1-2 inches) is dramatic but harder to clean. Decide on your preferred style before measuring, as it affects the final length you’ll order. Sill-length works in casual rooms; apron-length is versatile; floor-length is formal and makes rooms feel taller.

 

Where to Go From Here

Now that you understand rod placement, standard sizes, panel width, fullness, layering, and hem lengths, use our Curtains Calculator to determine the exact rod width and panel sizes you need. Enter your window dimensions, your desired rod overhang, curtain length preference, and the calculator will show you the rod size and panel widths to order.