DIY Supermarket

Perhaps the most important factor when it comes to fitting blinds so that they look like they were installed professionally and fit correctly is to ensure that the measurements you make are accurate. 

It is important to use a metal tape measure when making your measurements, as a plastic one is likely to stretch.  You should start by measuring the width and then move on to the height; this is because the width is what will be listed first when you order the blinds from the manufacturer.  Always be sure to write down your measurements immediately; you should never rely on your memory.

Additionally, if you are fitting blinds in a number of windows, you should measure all of the windows separately, even if it appears that they are the same size.  Room size, window placement and other factors may trick your brain into thinking that the windows are exactly the same size when the reality may be that they are not.

Finally, you should take the measurement for each dimension three times and, if there is a minor discrepancy, use the smallest measurement.  Windows are not always straight, and using the smallest measurement will help to ensure the best possible fit.