Measuring Vertical Blinds Correctly

Vertical blinds are a popular type of window covering in many situations to include French doors, sliding glass doors, and some windows. However, to ensure the windows look as beautiful as possible, it is important they be measured correctly. The information in this article can be used as a reference when you get ready to put up new vertical blinds.

Accurate Measurements

For starters, to ensure you get absolute measurements, be sure to use a metal or steel measuring tape over cloth or wood. Then, you will need to measure for the vertical blinds down to the nearest 1/8 of an inch. It would also be highly beneficial to write all the measurements down on payer, making clear notes to width and length. Sometimes, the numbers can get confused and then people end up with the wrong size vertical blinds.

Then, you will need to take the actual window opening for the right fit. Next, determine the type of mount interested in. An inside mount is one where the vertical blinds would be hung inside the window frame whereas an outside mount is installing the blinds on the outside of the wood frame. There is no right or wrong on this - it is simply a preference. However, there are some windows and doors that do not offer enough room outside, meaning only an inside mount would work.


While the inside mount on vertical blinds creates a cleaner look, the outside mount creates a much larger viewing area. Additionally, an inside mount for vertical blinds needs to have an opening large enough to ensure unobstructed depth. Then on the outside mount, you will need to allow for the height of the manufacturer's headrail, which changes from one product to another.

Inside Mount

For the inside mount on vertical blinds, measure the opening by going across the top where the headrail is located, going from the inside of the jamb and on the left-hand side of the jamb to the right side. For the length, start measuring at the top of the opening, taking measurements on the left, at the center part of the window or door, and then on the bottom. You could come up with three slightly different measurements, which is common so round down to the nearest 1/8 of an inch, using the smallest of the three measurements.

Outside Mount

Now for the outside mount for vertical blind installation, the width is measured for the area that needs to be covered by the blinds, but at the location where the headrail would be installed, again to the nearest 1/8 of an inch. Make sure the blinds do not overlap the opening at a minimum of four inches on either side. This way, you will gain better light control and privacy.

For the length on an outside mount, measure the area to be covered, again rounding down to the nearest 1/8 of an inch. The goal here is for the blinds to extend three inches above and below the window or door opening, or the molding around the window or door. Now, if you need to install vertical blinds that will go from the ceiling to the floor, just provide enough space for the flooring.