How to Calculate Stack Back Curtains

Things You\’ll Need

  • Metal tape measure

  • Calculator

Living room A longer rod for the stack back helps make the room look larger. Image Credit: Jupiterimages/ Images

When you want your pair of curtains to open fully to display the window and the view, a simple measurement and formula will help you calculate the stack back in front of the wall on either side of the window. Although a longer rod will cost more and take up more wall space, positioning an extended rod above the window trim helps make the room look larger. This formula will be your approximate guide to help you achieve an unobstructed view through your windows.

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Step 1

Measure with a tape measure the width of the window opening. Record this number.

Step 2

Divide this number by 6 to calculate the length of the rod extensions or the stack back on either side of the window. Work with a calculator, if necessary. Round up to the nearest inch. For example, a 48-inch-wide window opening divided by 6 equals 8 inches for the rod extensions on each side of the window. If your curtain is a single panel that pulls back to one side or the other, divide the window width by 3 to calculate the stack back.

Step 3

Add the window width plus the rod extensions for each side of the window in inches to calculate the rod length. In this example, 48 inches plus 8 inches for each side equals 64 inches. The face of the rod should measure approximately 64 inches to draw the pair of curtains off the window.


Factors such as the weight, lining and thickness of the fabric can affect how much of the curtain will actually stack in front of the wall. For example, a thinner sheer curtain will take up less space than a thicker damask curtain.


Avoid headers with tab tops or grommets, because these styles work best as stationary curtains.