The old adage — step twice, cut does not apply when measuring for window treatments. Rather, measure three times across the width and the length, and use the longest measurement for the most accurate calculations. When measuring for curtains, don’t forget to add one to three times the measurement’s width to acquire the curtain beam desired. Choose your place on the wall — underside of the window, to the floor, or midway between both for your final curtain length. And, last, but not least: Do not neglect to include hardware positioning measurements for hanging the curtain pole; write down all of your measurements.
Position the step stool or ladder as needed to achieve high enough on the window to create your measurements.
Pull the tape measure horizontally across the window width following securing it into the exterior frame by its tab or your fingers on top, bottom and middle of the window. Measure from the exterior of the window trim on one side to the other. If you haven’t mounted the hardware on which to hang the curtain, measure the distance from the exterior frame into the planned hardware place, double it and then add the result to the entire width measurement. As an example, if you hang hardware 2 inches beyond either side of the window frame, you need to add 4 inches to your entire figures for curtain width measurements. Round up each measurement to its closest 1/8-inch measurement and use the longest to your entire width.
Measure the window length from the top of the trim to the bottom in each corner and the center of the window. Write this down measurement. Add the dimension between the top of the window and the curtain pole to that particular measurement to your final curtain length for window-length curtains. If you plan to hang floor-length curtains, measure from the top of the rod’s place — or in which you plan to put it — to the floor. Once again, round up to the nearest eighth and use the longest of the 3 measurements for the final length figure.
Calculate the height of a valance, if you mean to hang one over the upper portion of the curtain. Divide the entire window length by four or three, dependent on whether you desire a valance that is one-third to one-fourth the height of the window. When selecting the figure that works to your valance, measure for the valance around the wall approximately 1 inch over the rod’s planned or known place, down the window length the necessary distance. As an example, if you have a window that is 48 inches tall, a well-balanced valance will equal 12 to 16 inches.
Run the tape measure across the width from the interior of the frame to its side on very top, middle and bottom. This measurement determines the width of the mini-blinds for an inside mount.
Extend the tape measure on the interior of the window from the top to its bottom to obtain the length that the mini-blinds will need to be. Step from the top to bottom in each corner and the center.
Step in three places for each measurement, top, bottom and middle, for the width, or each corner and the center of the window for the length. Utilize the most significant number for your final width and length measurements following rounding each measurement to the nearest 1/8 inch.