The exact steps for measuring windows can vary slightly depending on what style of window treatment you choose. So, before you pull out the tape measure, be sure to narrow down your choices to the style of window covering you’d like to order.

11 Common Window Measuring Mistakes

As we just mentioned, 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

First of all, 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 assume that the others are the exact same size.


We make 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. ALWAYS be sure to 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 ColorBlinds, 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 we hear about from upset customers and will lead to blinds that don’t fit.

You’re right in thinking that your blinds need to be slightly smaller than the window. But, 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. 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

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 below (in number 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.

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. If you don’t have one, pick up a full-sized tape measure and rest assured that you’ll be measuring accurately.

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. Even though you’ve seen TV woodworkers do this, it’s a big no-no if you want accurate measurements. Instead, we’ve got a secret to share with you. Look at the back of your tape measure for a small number. This gives you the exact size of the tape measure housing. If your tape measure doesn’t have a number like that, it may be low quality and less accurate. It’s probably worth it to pick up a name brand one from the store. Trust us, it’ll come in handy for lots of future projects.

Here’s how you use that little number to get an accurate inside measurement. Rest the metal end of your tape measure on one side of the window frame and extend until the housing rests on the other side. Note the measurement on the tape and then add the number from the back of the housing.

7. Not Reading The Tape Measure Correctly

If you’re not an experienced woodworker, you may not have looked closely at the tick marks on a tape measure or ruler since grade school. And that’s ok, we’ve got a refresher course for you. When you read the tape measure, simply count the hash marks after the last big number and use the chart below to find the correct fractional measurement.

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. If your windows are too shallow, call us at +264 61 30 20 30 for help finding a product that will work for your window. When measuring, also check to see if there are any obstructions in your window opening, like a security sensor or crank 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 for 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, they need to be slightly wider and taller than the opening. We recommend going at least 5cm wider than the opening on either side, so 10cm total. For the height, go about 8cm 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 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 mixed up the width and height.

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 and that you didn’t mix up width and height.


You’re Ready to Measure!

With all this in mind, you should be able to measure for blinds accurately and get a perfect fit. But hey, mistakes happen. If something goes wrong, you’re always welcome to consult our experienced team.

Is all this sounding too overwhelming? Colorblinds is here to help walk you through each step. Give us a call at +264 61 30 20 30, email us at or drop us a message on our Facebook Page for help.