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Curtain Rod and Panel Size Calculator

Measure the window wall once, then let this run the nine steps from our curtain guide: where the rod goes, how wide it spans, how wide each panel must be, and which stock length to order.

The window wall

6 to 12 in past the casing on each side lets open panels stack clear of the glass.

The curtains

For grommets, measure from the center of a grommet to the top edge of the folded panel. For rings, measure from the rod center down to where the panel top will hang.

How this calculator works

  1. Rod height: the gap between the casing top and the ceiling, times 0.67, added to the casing height. That puts the rod about two-thirds of the way up. With less than about 4 in of wall above the casing, a ceiling track works better than a wall bracket.
  2. Rod span: the casing width plus your extension on each side. Finials sit outside the brackets, so the rod you shop for is longer overall than this span.
  3. Panel width: the rod span times the fullness ratio for your header, divided by the number of panels. That is the minimum flat width of each panel.
  4. Panel length: rod height, plus or minus where the panel top sits against the rod, then the finish: minus 1/4 to 1/2 in to float, plus 1 to 2 in for a break, plus 3 to 6 in to puddle, minus 1/2 in at a sill, plus 4 in past the bottom of an apron.
  5. Stock size: the result is compared with the five lengths most stores sell, 63, 84, 96, 108 and 120 in, and the next size up is chosen, with the extra to hem or take up by raising the rod.

Floors and casings are rarely level. Measure rod height to floor at the left bracket, the center and the right bracket, and work from the shortest of the three.

Every figure here comes from our guide, Curtain Height, Width, and Length: The Numbers Before You Order, which explains each rule and the exceptions in full.

Sources