How to Measure for Window Blinds & Shades

Window Blinds & Shades

Adding blinds to a window treatment plan involves knowing how to measure properly for those blinds. The use of a blind is to shield the interior of your home from view and limit or control the light coming in from a window or glass-paned door. If you aren’t aware of how to measure these parameters then you could defeat the purpose of using a blind, to begin with.


Follow some simple rules and you should be successful in creating a new look for your windows. Start with being exact.

­- Use the right tools for the job. A cloth measuring tape will only bring you grief when installation time arrives. Always use a metal or steel tape measure. These tape measures hold an accurate measurement every time.

­- Measure to the nearest eighth of an inch, 1/8, and do not be too concerned when you discover windows that are not square. Construction is not always a precise art. Remember humans and time have some effect on your home. Warping and settling are common as are out of square windows. You won’t notice it once the blinds are in any way.

­- Always indicate which measurement is your width and which measurement is your height. Transposing numbers is a common occurrence for any human, and that includes you. Drawing a simple line drawing showing the ceiling the window shape and the floor line and indicating the ceiling and floor along with the direction of the measurements and then validating those is handy to have when you order the blinds. Help yourself with this process by measuring one or the other first every time.


Mounting your blinds inside the window opening is the recommended way to mount blinds for several reasons. First, it gives a clean flat look to the window and will not interfere with a drape or decorative treatment you may want to add at a later time. Second, if your intention is to control the light and viewing some of both is usually still possible with an exterior mounted blind. The choice is always yours.

When measuring for an inside mount always use an exact measurement and do not deduct. The manufacturer typically does the deduction for you so that the blind will operate easily.

For a width measurement, measure in three places and take the narrowest measurement as your final number.

For the height, again measure in three places and use the longest measurement for your final number. If you are using vertical blinds or privacy sheer blinds use the shortest height you measure.

Check with the manufacturer of your blinds to see what the minimum sill depth needed for installation is and for the product to be flush or flat across the plane of the wall (inset into the window frame). You may be able to eliminate certain brands by knowing this measurement up front. Measure your frame sill depth to see if you have the required space.


Typically a blind that is mounted outside the frame is mounted directly on the frame or further out and off the frame. This technique is sometimes used to hide ugly windows from view and always used if the window openings are too shallow to accept a blind installation.

Insuring maximum privacy and as little light as possible from seeping in will require you to add four inches or so to all sides. In addition, you must remember to leave room for the mounting hardware at the top of the blind. Know what measurement that is by checking with your manufacturer.

For width and height you must tell the manufacturer exactly what you want in measurements. They are not responsible for measuring your windows unless you have hired them to do so. Indicate it as an outside mount and that should tell them not to take a deduction on the numbers you have supplied.

Remember, your final numbers should be the width of the opening plus the additional measurements all the way around the blind for maximum privacy and minimum light plus the brackets to mount. If you are mounting the blinds off of the frame, consider the depth of the frame itself when measuring to make sure your brackets will extend far enough to clear the frame.

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