How to measure
When measuring for blinds, always go width 1st and length 2nd.
Do you want to hang the blind on the inside of the window or outside the window?
For Blinds (inside the drywall or frame) the Window (inside mount)
Order this if the blind is going inside (into) a window opening. The factory takes deductions for 1/8 up to 1/2 depending on the product. This is used so you do not need to think about the deductions necessary to put the blind in, install the brackets, etc. Basically, if your blind is going to fit inside an opening, just measure the window opening only and select inside the window and the factory will make appropriate deductions for that product. Width 1st, Length 2nd. Please note, on inside the window measurements, the factory takes deductions in order to fit inside that window opening. Top, Middle, Bottom Left, Middle, Right Write down the narrowest measurement (to the nearest 1/8) Write down the longest measurement (to the nearest 1/8)
For Blinds Outside(over the drywall or frame) the Window (outside mount)
Use this if the blind is going outside (over) a window opening. The factory takes no deductions or makes the blind slightly wider depending on the product.& You need to think about how much overlap you want on this window opening. For regular horizontal blinds, it is typically over lap on the width (add more to the opening width) and on the height (add more than the opening height). This will prevent light seepage, make room for the installation brackets, and provide privacy. For vertical blinds, extra on the width and extra on the height is normal.& Remember, this is just a typical estimation. You can make it any size you want. All mounting information can be viewed on the specifications link on that product page.Width 1st, Length 2ndPlease note, on outside the window measurements, the factory takes no deductions in order to fit that window opening