Anyone who has built just one home, or any building with home type windows, knows there is a big difference between using common window sizes and "custom" window sizes. Sadly, many plans come from designers or architects who disregard this very important point and it could result in plenty of wasted time and money. How so? Standard sized windows (and doors for that matter) are readily available "off the shelf" which means they do not need to be advanced ordered. Standard window sizes are also less expensive than their custom counterparts.
What difference does it make to the design?
In most cases, there is very little change to the appearance and function of the home when switching from a custom size to a standard size. With changes, usually only in a couple of inches, most interior elements will not be affected by switching. Obviously, there are times when the custom sizes will have to be used. Until then, we strongly urge you to consider using standard (stock) window sizes.
Here is a chart for a little guidance:
All of the above are common size (stock/off the shelf) windows.