Curtain rod length: what size rod do you need?

Last reviewed October 22, 2026

For a rod on the wall outside the window frame, add about 4 to 6 inches on each side of the frame: a 64-inch-wide window needs a rod about 72 to 76 inches long. For a rod inside the frame, the rod is as wide as the window between the inside edges of the trim.

What the guides recommend

• 4 to 6 in on each side: Taskrabbit's range. IKEA's guide asks for at least 6 in on each side.
• 6 in on each side, or the window width plus 20%: Kwik-Hang, a curtain hardware maker, gives both, so the curtains have room to stack back when open.
• About 6 to 12 in past the frame: The Shade Store's typical range for an outside mount, so curtains can be pulled fully off the window.

The guides agree on the reason: the extra rod is where open curtains sit, so they do not cover the glass. A wider rod lets more light in when the curtains are open; a narrower one fits a tight wall.

Inside or outside the frame?

• Outside mount (brackets on the wall): measure the frame from one outer edge to the other, then add your extension on each side.
• Inside mount (rod between the sides of the frame): measure between the inside edges of the trim. That is the rod length; there is no extension, and open curtains will cover part of the glass.

Rod length and adjustable rod size by window width

Outside mount, frame measured edge to edge. Each cell shows the rod length, then the first of the standard adjustable sizes Kwik-Hang lists (28–48, 48–84, 66–120, 120–170 in) that covers it. Other brands use other cut-offs, so check the range printed on the listing.

What the table assumes:

• The width is the outside of the window frame or trim, measured edge to edge.
• Rod length means the part the curtains hang along; finials on the ends add a little more.
• The size ranges are one maker's standard sizes. A length "at its maximum" fits, but leaves no room to adjust.

Worked example: a 72 in window

• 4 in on each side: 72 + 4 + 4 = 80 in; a 48–84 in rod covers it.
• 6 in on each side: 72 + 6 + 6 = 84 in; that is the very end of a 48–84 in rod, so a 66–120 in rod leaves room to adjust.
• Width plus 20%: 72 × 1.2 = 86.4 in; that needs a 66–120 in rod.

Then use the rod length as the rod span in the Curtain Panel Calculator to find how many panels and packs to buy. A longer rod needs more fabric for the same fullness.

Common questions

Should the rod be wider for heavy or lined curtains?

Thicker curtains take more room when they are pushed open. If you want the glass fully clear, lean toward the wider rules above (6 in or more on each side) and check how much space your curtains actually take when open.

What if there is a wall or a corner next to the window?

Use the space you have. Measure from the frame to the obstacle, keep the brackets clear of it, and use the same extension on both sides so the window looks centered.

Do the finials count?

Check whether the listed length includes the finials, and leave room for them at each end, especially near a wall.

What about a center support bracket?

Longer rods may come with a bracket in the middle. Curtains usually cannot slide past it, so treat each side as its own span when you plan panels; how to measure for curtains explains how. Follow the product's instructions for how many brackets to use.

How high should the rod go?

Width and height are separate choices. See how high to hang curtains for rod height by ceiling height.