Measure from the position where you want the drapery to start to the place where you want the hem, ideally the floor or one-half inch below the sill or apron. The result is your finished length.
Measure the glass width of the window on the left side of the corner, and then measure the glass width of the window on the right. Treat close-spaced window rows on each wall as a single window. Measure them from the left side of the leftmost window to the right side of the rightmost window.
Measure the distance from the corner to the window glass on the left, including the window molding. Measure from the corner to the window glass on the right. If the spaces on each side of the corner equal at least 20 percent of their respective glass widths, you need a pair of draperies that draw open from the center for each window. If the corner-to-glass spaces are less than 20 percent of the glass widths, treat the windows as one unit and use a single pair of draperies that draws open from the corner.
Double the distance between the corner and the window on the left. Add the glass width. Repeat with the corner-to-glass width on the right, and then add the glass width of the right hand window. The results are the lengths for each leg of the corner traverse rod you’ll need for corner windows that require two pairs of draperies. Make sure the rod has a two-way draw on each leg.
If you’re using a single pair of draperies for both windows, skip this step.
Add the left-side corner-to-window width to the left-side window-glass width. Divide the result by three, and then add that amount to the previous total. The final result is the length of the corner traverse rod’s left leg. Repeat with the right-side measurements for the length of the rod’s right leg. Make sure each leg of the rod has a one-way draw that draws away from the corner.
Skip this Step if you calculated your rod length.
Calculate the finished width of each panel separately for corner-window draperies. If you’re using two pairs of center-drawing draperies, divide the rod’s left-leg length in half. Add 3.5 inches to the width of the panel next to the corner for overlap. Add 3.5 inches plus the rod’s return to the width for the finished width of the panel farthest from the corner. Repeat with the rod’s right-length, unless both legs are identical. For a single pair opening at the corner, add 3.5 inches plus the return to the leg length for the finished panel width on each side of the corner.