Common Window Measuring Mistakes

Measuring Mistakes You Can Learn From: 

The most important thing is to follow the measuring instructions for the specific style of window coverings you are ordering. However, we'll share some common mistakes that apply to most styles.

1. Assuming That Similar Windows Are The Same Size

Let's set the record straight, there is no such thing as a "standard size" window. Just because all the windows in your room look like they are about the same size doesn't mean that you can measure one and that size for the whole order.

The Blue Space makes all of our products to your exact measurements, down to the millimetre. Windows can have small variations due to framing or your house settling over time. That being said ALWAYS measure each window separately for your order.




2. Measuring The Size You Want Your Blinds To Be, Not the Size Of The Window Opening

When you order inside mount window coverings from The Blue Space, we always ask for the EXACT size of the window opening, edge to edge. Some people may make their measurements slightly smaller thinking that their blinds need to be slightly smaller to fit in the window. This is the BIGGEST MISTAKE and will lead to blinds that don't fit.

All of our blinds and shades require slightly different deductions to height and width for the perfect fit. To keep things simple for our customers, we do all of those calculations for you at the factory. Just give us the exact size of the window opening and we'll make blinds that fit perfectly.


3. Measuring The Old Blinds Rather Than The Window Opening

Similar to #2, some people assume that if they measure the old blinds in their window, they'll receive the exact same size. However, the measurements are based on the window opening and will come in too narrow if you do this. Use the technique in #4 to get it right.

Also, don't assume that you can re-use the old brackets or simply measure the distance between the brackets. Always measure the window opening from edge to edge.


4. Not Measuring In 3 Places

One of the most important steps is to measure both the height and width in 3 places - top, middle, and bottom. This allows you to be sure your blinds will fit, even if your windows are a different size at the top or bottom of the opening. Just as we said that no 2 windows are the exact same size, it's rare to find a window that's perfectly square.

If your windows are tall and the top is out of reach, it's still important to get out a ladder and measure at the very top. You'd hate to skip that step and not have blinds that fit.

Record all of these measurements on the notepad and then use these guidelines to choose the right measurement.


  • For Roller Shades, Roman Shades, Aluminium Venetians, or Vertical Blinds use the measurement from the top of the window.
  • For all other styles, when fitting in recess use the narrowest width measurement of the top, middle and bottom.


  • For Roller Shades, Aluminium Venetians, Shutters, Panel glide or Vertical Blinds choose the shortest height.
  • For all other styles, use the longest height.

5. Not Using A Steel Measuring Tape

When measuring your windows, because we make your window treatments to the millimetre, it's important to have super accurate measurements. A ruler, yardstick, cloth tape measure for sewing or just eyeballing it won't do!

The only way to get correct measurements is to use a steel tape measure. Also, be careful with the pocket-sized freebie ones you may have lying around. These can be less accurate than what you find at the home improvement centre.


6. Bending The Measuring Tape

You may think that the only way to measure inside an opening (like your window) is to bend the tape measure and try to guess what tick mark is in the middle of the curve. If you are not confident in measuring this way.

Look at the back of your tape measure for a small number. This gives you the exact size of the tape measure housing. Once you have placed the Tape into the window space as shown below write down the measurement on the tape and then add the number on the back of the tape measure to your measurement. Don’t forget to add this for each measurement.



7. Not Reading The Tape Measure Correctly

If you're not an experienced measurer, you may not have looked closely at the tick marks on a tape measure or ruler since high school. Each tick is 1mm so when you measure, select the closest one to the body of the tape measure that is visible and make a note.

Once you have done that don’t forget to add the body of the tape measure if you are using that method.


8. Not Measuring Depth

For an inside mount, width and height are not the only measurements that matter for your windows. Depth is essential for determining if your blinds will protrude out of the window, or if they can be mounted at all.

Measure your window depth from the glass to the edge of the window opening. Then check the product specification section on your product page to find the minimum inside mount depth dimension. This is the minimum depth you'll need to install your product. When measuring, also check to see if there are any obstructions in your window opening, like a security sensor or window handle. Measure your depth from the edge of the obstruction forward and then compare to the minimum inside mount depth dimension.


9. Not Adding Width To Outside Mount Blinds

Measuring outside mount blinds is a different process. In this case, you won't measure the size of the window opening, but the exact size that you would like the product to be.

Because you're mounting the blinds outside the window on the wall above and not on the architrave, they need to be slightly wider and taller than the opening. We recommend going at least 40mm wider than the opening on either side, so 80mm total. For the height, go a minimum of 50mm above the window trim (to allow for the mounting brackets) and measure from that point down to the window sill.

Without adding these extra centimetres, your window covering may have gaps on the side where the light shines through, or not fully reach the window sill.


10. Mixing Up Width And Height

You wouldn't believe how often people get the wrong size blinds simply because they write the wrong size first. Always write your measurements as Width x Drop.


11. Not Checking Your Measurements Twice

Before you place your order, it's always a good idea to double-check your measurements. As they say in the building trades, "Measure twice, cut once." Make sure that you read the tape measure correctly, measured in 3 places, selected the right measurement of the 3, didn't mix up width and height, and that you transferred your measurements to your The Blue Space order correctly.



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