Let’s get started! Using a steel measuring tape for accuracy, take exact measurements, rounding up to the nearest 1/8” inch. Start with the width and then measure the length. Be sure you correctly label which is width and length.

Measure every window in the room. Just because they are supposedly the same does not mean they truly are. You should also measure the width at the top of the window as well as at the bottom, as they can also differ. Measure the wall space to the left, right, above and below the window. This tells you how much wall space you have for stacking and returns, etc. It also will tell you the total measurement you will need for length.

For full-length drapes, be sure to add the window length to the wall space below the window. Then you will need to add for the wall space to be covered at the top of the window. This is your total finished length. The total finished width is figured through the same process, only horizontally (the window width, plus wall coverage left and right).

A blind or shade that will be mounted on the inside of the window frame is an IBM, or inside mount. Most reputable blind and shade manufactures will make allowances for the mounting hardware. Note: You must let them know your measurement is IBM exact. Please ask this question in case their procedures may differ from the norm. 

Blinds and shades that mount on the outside of the window frame are called OBM’s, or outside mounts. Allowances for the mounting hardware are not usually needed. There could be an exception, however. Take for instance a right-angled corner window. Again, when you order tell them you want and outside mount “OBM,” unless you have an unusual situation like a right –angled corner window.

With these few simple tips and information you should be able to correctly measure your windows for custom or ready-made treatments. If you have a particularly difficult or unusual window configuration I would encourage you to consult with a professional before attempting to install expensive window treatments in your home. However, the standard, basic window styles in most homes can be measured and treated by the home decorator. Get the measuring tape out, and let’s go!!

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