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How to Measure Windows for a New Shades

Automated Shades

So, you’re thinking about getting new window treatments and you want a better idea of what you’ll need. Measuring a window accurately before purchasing a new blind or shade is essential to ensuring your investment will fit and function correctly. Though you’ll want a professional to come in and take measurements prior to installation or customization, here’s a guide on how you can do it yourself prior to meeting with a window installer, or when the situation requires.

What you’ll Need:

  • Steel measuring tape (don’t use fabric measuring tape, as they can stretch).
  • Paper and pencil
  • Ladder (if required for your window height)

The first thing to determine is where your new blind or shade will be installed. For example, some window treatments are mounted inside the window frame, and others are mounted outside the frame. You will need at least ¾” of an inch in depth to mount a blind inside the window. This minimum depth will vary depending on the type of window treatment you ultimately select.

If blocking out as much light as possible is one of your main objectives, mounting on the outside is the easiest way of achieving this. Many times when mounting treatments inside the window frame. it results in slight gaps around the edges of the blinds that let in light. A professional installer has the skill and customization ability to reduce those gaps.

Create a visual of your window

The next thing you’ll want to do is sketch your window on paper and make notes of important details, such as trim, potential problem areas, window sills that extend beyond the frame, etc. This will give you a visual record to reference and remember your window’s dimensions, and really comes in handy when trying to discuss your needs with a window treatment dealer.

With your metal measuring tape, measure the inside of the window frame (if mounting window covers inside), near the top where your covers will be mounted. Measure from one side to the other, to the nearest 1/8″, then add these measurements to your drawing. Next, measure the two other points between the sill and top of the window frame in the same fashion and write them next to your drawing. If the measurements aren’t exactly the same, you can use the smallest measurement as your width, so the shade can operate properly.

To get an accurate measurement of the height, measure from top of sill to top of window frame in (at least) two different locations. Add these measurements to your sketch, and if there’s any variance in the measurements, use the smallest as your length.

To check the squareness of your windows, measure from one corner diagonally to the other. Do this in both directions. Write down the measurements and then compare. If they are more than 1/2″ different, your window is out of square. In this case, you will want to mount your shade on the outside of the frame – if mounted inside the frame, it may not operate properly.

For an outside-mount shade, follow the same instructions listed above, except measure from the outside edge of the window trim on one side, to the outside edge of the other side. If the trim varies in width, use the widest points as your measurement. Add at least 1″ to each side of the window (2″ total addition to the width of your shade) to overlap the trim slightly. This will ensure your shade covers the trim completely. At the top, you may may to add 2″ or more to the total length; make sure you have enough length figured into your measurement to accommodate your mounting bracket, as it needs flat wall space for installation. You should now have the proper measurements to order your new window treatment!

Some helpful tips:

  • It is a good idea to purchase your window treatments from a reputable dealer who will take final measurements for you. This will put the responsibility for errors on the dealer, not you, and will keep you from reordering (and paying for!) mistakes in measurements.
  • Make sure to always use appropriate caution while using ladders when measuring your windows– don’t overreach or place ladders on uneven surfaces.
  • If you’re dealing with specialty shaped window such as bay or bow windows, or arches, angles, OR you’re in a hard to reach location, your best bet is to have a professional come do it. Your window installer might have to make a special templates before ordering your shades.
  • For the most accurate measurements, get assistance from a family member or friend if your windows are wide; having someone to hold the end of the measuring tape will make sure you’re getting an accurate number.
  • Don’t make any reductions to your measurements to allow room for operating your shades. Any deductions to measurements will be handled by the shade manufacturer. If you also deduct from the width or length of the shade, you could end up with light and privacy gaps.


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