Measuring for double windows requires a methodical approach to ensure your curtains frame the architectural feature beautifully. One common mistake is treating the two windows as a single unit, which can result in curtains that look too small or awkwardly centered. The goal is to create a balanced, unified look that enhances the width of the entire bay while maintaining the individual functionality of each panel.
Understanding Double Window Layouts
Before you grab a tape measure, it is essential to identify the specific configuration of your double windows. Not all double window setups are symmetrical, and recognizing the structure dictates your measurement strategy. The way you measure a classic pair of equal-sized windows flanking a fixed center panel differs significantly from measuring asymmetrical garden windows or sliding configurations.
The Classic Pair
The most straightforward layout consists of two identical windows placed side-by-side, often with a shared header or mullion in the center. For this arrangement, you treat the combined width as your total curtain width. However, you must decide if you want one large panel spanning the entire width or two separate panels stacked behind one another. For a luxurious, full look, you will likely want to treat the two panels as one wide window, using the combined measurement to calculate fabric fullness.
Asymmetrical and Architectural Setups
More complex architecture might feature a picture window on one side and a sliding window on the other, or a wide fixed window paired with a narrow operational one. In these scenarios, measuring becomes about visual balance rather than strict mathematical equality. You might choose to hang curtains only on the operable side to mimic symmetry, or you might hang them wider than the frame to draw the eye away from the imbalance.
Measuring for Width and Height
Once you have identified the layout, you need precise measurements for width and height. Width determines how much fabric you need, while height determines where the curtain rod hangs and where the hem falls. Always measure both windows independently first, even if they look identical, to account for any construction variations.
Taking the Width Measurement
To determine the width, measure the total distance from the outer edge of the left window frame to the outer edge of the right window frame. Place the tape measure at the top of the frame, run it straight across to the top of the opposite frame, and then repeat this at the bottom. Jot down the largest of these two measurements; this accounts for any slight warping or unevenness in the header. If you plan to mount the rod significantly above the window frame, extend the measurement upward to the intended rod height to ensure the brackets have enough space.
Determining the Hanging Height
The vertical measurement is just as important as the horizontal one. The standard goal is to hang the rod approximately 4 to 6 inches above the window frame and to extend the curtain stack (the folded fabric at the center) far enough beyond the window frame to allow the panel to close fully without blocking the glass. Measure from the top of the frame to your desired rod height. If you are installing a rod that sits closer to the ceiling to create the illusion of taller windows, measure from the ceiling down to the bottom of the window frame to determine the length of the curtain.
Calculating Fabric and Hardware Needs
With your width and height measurements noted, you can determine the quantity of fabric and the size of the hardware required. This step prevents the frustration of buying beautiful fabric only to find it is not wide enough or that the rod is too short for the intended stack back.
Fabric Width and Fullness
Curtain panels look best when they are gathered or "full." A general rule of thumb is to have a curtain width that is at least 1.5 to 2 times the width of the window or rod. For example, if your measured width between frames is 80 inches, you should aim for a total curtain width of 120 to 160 inches. If you are using a single panel to cover the double window, you will need to find a fabric wide enough to accommodate this fullness (custom sewn panels are often necessary). If you are using two panels, divide the total desired width by two to determine the width of each individual panel.
Rod and Hardware Sizing
The curtain rod must be longer than the window frame to allow the curtains to stack properly. Select a rod that is at least as long as your total measured width, but extending 8 to 12 inches beyond the frame on each side is ideal. This overhang creates a balanced look and allows you to pull the curtains completely out of the way. Ensure the brackets for your double windows are heavy-duty and spaced correctly; typically, brackets are placed at the edges of the frame and one in the center of the combined width to support the weight of the panels.
Final Checks and Adjustments
Before you cut any fabric or drill any holes, stand back and visualize how the curtains will interact with the room. Consider the purpose of the room—whether you need maximum light control or sheer privacy—and factor that into your measurements. Remember that the measurements you take are the foundation, but the way the fabric drapes and hangs will be the final judge of a professional finish. Taking the time to measure double windows accurately is an investment in the aesthetic harmony of your space.
