How to Measure Arch Window Shades and Blinds

Large Arch Window

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Windows arches make your home look attractive from the inside and out and help break up the monotony of rectangular windows. However, the curved nature of the arches can make them a bit tricky to measure if you want to put up window treatments. In this guide, we walk you through identifying your type of window arch and explain how to measure arch window shades and blinds.

Determine What Types of Arches You Have

The first step to measuring for arch window shades is know what types of arches you have. There are five kinds of window arches you should know:

  • Perfect arch: A perfect arch has a height exactly half the length of the width. Basically, if you took a circle and chopped it in half, you would get a perfect arch; hence, the name.
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  • Palladian arch: In a palladian arch, the height is greater than half the width, resulting in a dramatic appearance. A palladium arch is taller than a perfect arch. You will want to be especially sure your palladium arch treatment has a strong base mount since it is taller than the other options listed here.
  • Eyebrow arch: In an eyebrow arch, the height is smaller than half the width, creating a flatter curve. An eyebrow arch is shorter than a perfect arch.
  • Eyebrow arch with legs: This is a variation of the eyebrow arch, where straight “legs” extend beneath the arch—picture a rectangle topped with a curve. For this type of window arch, you will need to measure the legs as well as the arch itself.
  • Quarter arch: This style of arch is one half of a regular arch and a quarter of a sphere or oval; hence, the name. A quarter arch is formed of a right angle with the arch across from it. A quarter arch may be perfect, or it may be elongated in either direction. It may also have legs that extend from the bottom.
second floor landing

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How to Measure Arch Window Shades and Blinds

Now it’s time to grab your steel tape measure and get to work. First, measure the bottom of the arch at the widest point, taking the measure to the nearest ⅛ inch. At this point, don’t measure the trim, only the window opening. Do the same with the height—measure it to the nearest ⅛ inch at the highest point. Make a note of both measurements.

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If your arch has legs, then you should also measure the height of those to the nearest ⅛ inch. Make sure to measure them separately, as one may be a bit longer than the other. Uneven windows are common in old houses and other buildings where the frame may have settled.

If you are planning to inside mount your living room window blinds, you can use the measures you have just taken. Do not take deductions yourselves; Factory Direct Blinds and other manufacturers will take any deductions necessary to make it fit. If you preemptively make the deductions, your window arch treatment will be too short.


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For outside mount blinds that overlap the window trim, you will need to make additions to the measurements. First, examine the bottom and determine where you will mount the arch window treatment. If you are planning to outside mount dining room blinds on the bottom window as well, be sure to leave enough room so the two sets of hardware will not bang into each other. Once you figure out how far the mounting hardware will go below the window, add that amount to the height.

Next, decide how far you want the shade to extend above the window arch. We usually recommend at least three inches of overlap at the top for privacy. Do the same with the sides of the window. We recommend at least two inches of overlap on each side, for a total of four inches of extra material. Keep in mind, deductions are not taken on outside mount window treatments, so the measurements you put in will be the measurements you get. Make sure they are accurate before hitting the “order” button!

We hope this cleared up how to measure for arch window shades. If you’re looking to purchase multiple types of window treatments at once, be sure to check out our complete instructional series, including how to measure for mini blinds.

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