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How to Measure a Window for Window Treatments

Before shopping for new blinds or shades, you need to know exactly how your new window treatments are going to fit over or in your window. The best way to do this is to take the measurements yourself.

To start, make sure you have a steel tape measure. Steel tape measures provide the most accurate results and can survive more wear and tear than fiberglass tapes.

Is There a Standard Window Size?

You may assume windows come in a standard size, but we’re here to clear up the misconception. There is no such thing as a “standard size” window. Likewise, just because all the windows in one room appear to be the same size (yes, even if they’re right next to each other), you should make sure to measure all three.

Outside-Mounted vs. Inside-Mounted Window Treatments

You’ll have to take a different set of measurements depending on the style of window treatments you’re going to get. Inside mounts usually provide a clean look and sit neatly within the window frame. Outside mounts, however, can give the illusion of a longer, wider window or help hide an unattractive window frame.

Should I Measure for an Inside or an Outside Mount?

Many of the same principles apply for inside versus outside mount applications. The difference with an outside mount is that you can build out the frame and add depth where you want it.

Inside-Mount Measuring

Inside-Mount Measuring

If you’re getting an inside mount, you’ll need to measure the exact width of the top, middle, and bottom of the window. Whatever the results are, use the narrowest width to determine the window width. Next, measure the exact window height on the left, in the middle, and on the right. Use the longest height in this case, if there’s any variation.

Outside-Mount Measuring

Outside-Mount Measuring

For outside mounts, measure the exact width where the window treatments are to be placed. For example, if you’re installing blinds, measure the width where the proposed headrail will be sitting. Add about 3 inches of overlap for privacy and better light control (the three inches should be 1.5 inches on the right and 1.5 inches on the left of the window). To measure height, measure from the top of the proposed headrail location to the base of the sill. If you have no sill, measure to where you want the blind to fall. Add 1.5 inches to the final measurement for better light control.

Measure Twice

Measuring a Window

Remember the proverb “Measure twice and cut once”? It’s a carpentry rule of thumb meant to prevent people from making a mistake they can’t take back. After you take all your measurements once, retake them just to be sure.

Mistakes to Avoid

  1. Forgetting to measure the width of your windowsill: If you have a windowsill, having that measurement might also help you determine whether or not a set of blinds or shutters will fit in the window.
  2. Misusing the tape measure: You shouldn’t have to bend the steel tape at all to get a proper measurement. To get an accurate measurement, rest the edge of the metal tape measure dispenser against the edge of the windowsill or area to be measured. There should be a small measurement on the tape measure, which you should add to the total.
  3. Mixing width and height: It’s easy to get the two confused if you don’t mark them down correctly, which is why it’s helpful to double-check your measurements.
  4. Not adding width to outside mount blinds: If you’re mounting blinds outside the window, you do not measure the window opening. Instead, you should measure the exact size you need the product to be. The width measurements should typically be 2 inches wider than the opening on either side (4 inches total). The height should start about 3 inches above the window trim, which allows for mounting brackets. Without the extra inches, you risk gaps in the window treatments where the light will shine through.
  5. Not measure to the exact 1/8th of an inch: Windows can have small variations because of the framing or from your house settling on its foundation over time. Always measure each window separately, even if two or more windows appear to be the exact same size.
  6. Measuring the existing window coverings inside of the window opening itself: You may think you just need to measure for the size you want the blinds to be. Do NOT do this. You should always measure for the exact size of the window opening, edge to edge. Don’t make the mistake of thinking your blinds company wants to know the size of what the blinds should be – leave that to us!
  7. Not measuring for 3 places for each window: height, width, and depth. Depth is particularly important based on whether you’re measuring for an inside or an outside mount.
  8. Not using a proper measuring tape: Rulers, cloth measuring tapes, or yardsticks need not apply! You should always use a steel measuring tape. If you don’t have one already, pick up a full-sized steel measuring tape at your local hardware store.

Windows aren’t all the same size, so measurements are essential to getting your custom window treatments done correctly. If you’re unsure about the measurements, you could always call our team at Bloomin’ Blinds. We provide custom window treatments that satisfy our customers nationwide. Our professional window treatment installers understand precisely how to measure the windows in your home for whatever effect you’re looking for. From blinds to shutters to window draperies, we handle it all. Call us to schedule a free estimate today!

Kevin Stuart About the Author: Kevin Stuart, Bloomin’ Blinds
Kevin has been a part of the Bloomin’ Blinds team since 2004. He is an expert in window covering repairs and has been known to finish even the hardest repair in 12 minutes and 26 seconds (the fastest Bloomin’ Blinds repair time yet). Kevin loves puzzles and values fixing things and bringing smiles to the faces of his clients.