Arched windows may seem difficult to measure, but with the information below you’ll find it to be an easy task. There are several styles of arched window, and measuring guidelines vary somewhat between styles. If your style is not listed below, call 800-505-1905 and one of our design experts will help you get the right measurements!

Helpful Hints Before You Begin Measuring for Arches:

  • For the most accurate measurements, only use a steel tape measure.
  • Don’t mix up width and height measurements. Always follow the width by height format (W x H) and mark them as such.
  • Measure to the nearest 1/8 inch. Never round up or down to the nearest half or whole inch.
  • If you’re measuring for more than one window, measure each one individually – never assume that your windows are the same size, even if they may look alike.
  • Cellular (honeycomb) shades and pleated shades: Side mounts are upon request only and are not available for arches wider than 40”.
  • Minimum window opening depth for inside mount is 1 ½”; if you want your window covering fully recessed (not sticking out of the window opening at all),  minimum depth is 2 ¼”.
  • Make sure you have a good mounting surface at the base of the arch as most arches are bottom mount only.

Perfect Arch

To be a perfect arch, the height must be exactly half the width. If not exact, it’s considered a non-perfect arch. In some cases, you’ll need to provide a paper template of your window. Please call us at 800-505-1905 for more information.

  1. To find the width, measure from left to right at the bottom of the arch. If you plan to mount a window covering below the arch (arches often sit atop another window), take into account where each window covering will need to mount.
  2. For the height, measure from the very center of the width to the highest point on the arch.
  3. For an inside mount, order your product in the exact measurements you took, with no deductions. The factory will apply deductions when making your product. For an outside mount, add 2” to both the width and height. Your product will be made to the exact measurements you specify.

Palladian Arch

This style arch is when the height is more than half the width. The arched part is steeper compared to the perfect arch.

  1. To find the width, measure from left to right at the bottom of the arch. If you plan to mount a window covering below the arch (arches often sit atop another window), take into account where each window covering will need to mount.
  2. For the height, measure from the very center of the width to the highest point on the arch.
  3. For an inside mount, order your product in the exact measurements you took, with no deductions. The factory will apply deductions when making your product. For an outside mount, add 2” to both the width and height. Your product will be made to the exact measurements you specify.

Eyebrow Arch

An eyebrow arch will be shorter in height than a perfect arch.

  1. To find the width, measure from left to right at the bottom of the arch. If you plan to mount a window covering below the arch (arches often sit atop another window), take into account where each window covering will need to mount.
  2. For the height, measure from the very center of the width to the highest point on the arch.
  3. For an inside mount, order your product in the exact measurements you took, with no deductions. The factory will apply deductions when making your product. For an outside mount, add 2” to both the width and height. Your product will be made to the exact measurements you specify.

Eyebrow Arch with Legs (also known as Elongated Arch)

This style has two vertical sides leading up to where the arch starts. The sides are called legs. You will take four different measurements for this style.

  1. To find the width, measure from left to right at the bottom of the arch. If you plan to mount a window covering below the arch (including the elongated or “legged” portion), take into account where each window covering will need to mount.
  2. For the height, measure from the very center of the width to the tallest point of the arch.
  3. Measure each leg's height from the base to the point where it starts to curve into an arch. Make sure to measure both, as the legs may have slightly different measurements.
  4. For an inside mount, order your product in the exact measurements you took, with no deductions. The factory will apply deductions when making your product. For an outside mount, add 2” to both the width and height. Your product will be made to the exact measurements you specify.

Quarter Arch (Perfect, Non-Perfect, Elongated)

A Quarter Arch is one half of a regular arch. It will consist of a right angle with the arched section across from the right angle. In some cases, you’ll need to provide a paper template of your window. Please call us at 800-505-1905 for more information.

  1. To find the width, measure from left to right at the bottom of the arch. If you plan to mount a window covering below the arch (arches often sit atop another window), take into account where each window covering will need to mount.
  2. For the height, measure the straight side, from the base of the arch to the tallest point.
  3. For an inside mount, order your product in the exact measurements you took, with no deductions. The factory will apply deductions when making your product. For an outside mount, add 2” to both the width and height. Your product will be made to the exact measurements you specify.
  4. Make sure you have a good mounting surface on both the bottom and the side, as this arch style may require mounting on both sides.

How to measure for quarter arches