Curtain Stack Back Calculator
When curtains open, the fabric doesn't disappear — it gathers into a stack on the wall, and if the rod isn't wide enough, that stack sits on your glass, blocking the light and the view the window exists for. This calculator estimates the stack for your header style, fullness, and fabric weight, then tells you how wide the rod should be and how far past the frame it should extend so open panels clear the window entirely. The numbers are honest workroom estimates, not lab measurements — when in doubt, a rod an inch too long costs nothing. Once the rod width is settled, the curtain size calculator turns it into exact panel dimensions.
Common Questions
How far should a curtain rod extend past the window?
Far enough that fully open curtains sit on the wall, not the glass — which depends on how much fabric you're stacking. The decorator shorthand of 4–6 inches per side is a minimum for light, pleated panels; a full pair at 2× fullness typically wants 10–15 inches per side for genuine glass clearance. This calculator does the estimate for your exact header, fullness, and fabric weight.
How much wall space do open curtains take up?
As a working rule, open drapery stacks to roughly a quarter to a third of the rod's width in total, split across both sides for a center-open pair. Sewn pleats compress tightest, grommets hold a fixed wave they can't compress past, and gathered rod pockets stack deepest of all.
Do pleated curtains stack tighter than grommet?
Yes, meaningfully. Pinch pleats are sewn to fold accordion-style, so the fabric collapses into orderly columns; grommet spacing enforces a minimum wave depth that never fully compresses. In our model pleats stack to about 15% of their flat width against 20% for grommets — on a wide window that difference is several inches of glass.
What is stack back on curtains?
Stack back is the wall zone where curtains gather when fully open — the width of the 'column' of fabric beside the window. Planning it is the difference between a window that opens to its full glass and one that permanently loses its outer few inches to fabric.
Should both sides of the rod have the same stack back?
Only if the curtains split to both sides. A center-open pair stacks half its fabric on each side, so the rod extends equally. A one-way draw — common on sliders and corner windows — stacks everything on one side, so all the extension belongs there, with just finial clearance on the other.