What size curtain rod do I need?

Drape & Dawn earns a commission from qualifying purchases made through links on this page, at no extra cost to you. It does not change what we recommend. Full disclosure.

Diameter follows the weight more than the span. Use 5/8 inch only for sheers and short windows. Use 3/4 inch for standard lined panels on ordinary spans. Use 1 inch for anything blackout, thermal or wide. Wall thickness matters as much as the stated diameter — a lock-seam steel tube is considerably stiffer than a thin-wall one of the same size.

Center supports are decided by span alone. Over about 60 inches, fit one. Over 96 inches, fit two. This is the cheapest fix for sag in the whole category, and it means a lighter rod will do a job that would otherwise need a heavier one.

The rod width you calculated assumes you have that much wall. Two situations regularly break it: a window close to a corner, and two windows close together. In the first, extend as far as you can on the open side and accept less on the tight side — asymmetry here is far less noticeable than a rod that does not fit. In the second, consider one long rod across both windows, which usually looks deliberate and gives you the stacking room neither window has alone.

Also check the projection: how far the rod stands off the wall. It has to clear the window frame, any blind headrail behind the curtain, and a deep sill if you have one.