You need to decide the place of mounting, i.e., inside or outside the frame, to determine the size of the blinds for a 34.5 inches window. If you go for an inside mount, take three measurements, and ask the manufacturer to make the desired deductions.
On the other hand, if you want to go for outside mount window blinds, you would like to add a few inches to both the width and height. In that case, you can choose a blind measuring 34.5 + 3 = 37.5 inches. Meanwhile, a blind measuring 37 inches will also do.
Here are some DIY tips for the measurement of the window frame and determining the size of the blind.
- To determine the exact size of blinds you need for your windows, measure the width of the window frame at three different places, i.e., the top, middle, and bottom.
- Use the narrowest measurement for the size of the blinds you need to shop. For a window that is 34.5 inches wide, look for blinds that are at least this wide for the inside mount.
However, for an outside mount, it is generally recommended to add a few inches to the width of the window to ensure that the blinds will fully cover the window frame and have enough overlap to completely block out light.