How To Measure For Blinds

Before you purchase blinds, you need to ensure you get the right size and design for your windows. Let’s take a look at how to measure windows for blinds, so you have a perfect new look for your home.

Window Measuring Tips

When measuring blinds, there are a few tips to keep in mind. 

  • Use a good-quality construction measuring tape made of steel to ensure accuracy (link to Amazon). 
  • Measure to the closest ⅛”. If it’s closer to 1/16″ round down to the nearest ⅛”. 
  • Include valances and hardware in your height measurements so you don’t end up with short blinds.
Outside mounted roman shades
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Outside vs. Inside Mount Blinds 

Blinds can mount on the outside or inside of your window frame. Outside mount blinds secure over your window frame, hiding old or unattractive window frames. They’re also an excellent solution for shallow window frames that can’t contain the blinds properly. Outside mounted blinds don’t require curtains or drapes and usually block out light well enough on their own.

Inside mount blinds mount inside the window frame utilizing a headrail that secures to the frame’s top. Many people use drapes to help block excess sunlight. This blind style emphasizes the window’s height and decorative molding.   

How To Measure for Outside Mount Blinds

Outside mount blinds are versatile enough to work on all window types and sizes. When installing external mounts, you can secure the headrails to the window molding or the wall. When blinds are mounted to the outside of a window frame, they will hide the entire window, including the frame. Generally, if there is no frame to your window, an outside mounted blind can be ideal.

Measuring a window for outside mount blinds


Before you install your outside-mounted blinds, you will need to get the proper measurements. You need to measure the window casing width and height. 

First, measure the width of your window from one side to the other. 

Next, measure your window’s height. Measure from the top of your window casing to the window sill. You need 2″ of flat space, either on the wall or the molding for the headrail.  

Outside Mount Overlap

Because outside blinds mount on the outside of your window, many people want excess material for an overlap. This overlap means having a blind that’s larger than the size of your window frame.

Reasons you may want extra material for your blinds are to get more privacy or to block out excess sunlight that can shine along the edges. 

For blinds, mini blinds, or shades, about 1.5″ overlap on each side is a good starting point. A 2″ overlap (or even a little more) is better for vertical blinds, roller blinds, and solar shades. You can go as far as you’d like, too. Sometimes, it can be transforming to make your room appear to have a very large window simply by hanging an over-sized blind. This is, of course, a matter of taste and design. It may or may not necessarily make the room appear larger.

How To Measure for Inside Mount Blinds

When measuring for blinds that mount inside your window, you will need to take measurements differently from outside blinds. 

How to measure a window for inside mount blinds

To measure the area for inside blinds, start by getting your depth dimension. Use your tape measure to see how deep your window sets back. This step is crucial because your headrail will mount to the inside of your window frame, and you want to make sure there’s enough room.

Next, you’ll want to measure the window frame’s width. Check the frame’s size at the top, the middle, and the bottom inside edges. Some windows are not perfectly square. 

And finally, check the window frame’s inside height. Repeat the process of doing three measurements on the inside of the frame. Measure the left side, the right side, and the middle. Use the longest measurement for the length of the new blinds.

How to Measure for Vertical Blinds

Vertical blinds have slats that run up and down instead of horizontal, or on top of each other. This style of blinds can mount inside or outside the window, provided there is sufficient room. 

To measure for inside vertical blinds, start by measuring the inner width at three places – bottom, middle, and top. Round to the closest ⅛ of an inch. Then repeat the measurement process for the height, checking the right, left, and center. And finally, measure the depth. 

To measure for outside vertical blinds, start with measuring the width, leaving an extra 4″ on each side for overlap. Next, measure the height to the nearest ⅛”. Remember to leave 2″ of excess space over the window for your brackets. 

How to Measure for Mini Blinds

Mini blinds are horizontal window blinds with long, narrow slats. This blind style can mount on the inside or outside of the window frame.

To perform measurements for inside mounted mini blinds:

  1. Start by measuring the width on the inside of the frame, left to right, getting sizes for the bottom, top, and middle.
  2. Measure the height, starting at the top left.
  3. Use the largest of the three measurements, rounded to the nearest ⅛ of an inch.

To measure outside mounted mini blinds, determine the window’s width, extending your measurements past the trim left to right. For windows without trim, add an extra 2″ for overlap. Then, determine your height. For protruding sills, start the measurements 2″ below the sill and 3″ above the frame. 

How to Measure for Roman Shades

To measure your windows for inside mount Roman shades:

  1. Start by measuring the frame’s depth.
  2. Determine the window’s width and height.
  3. For width, use the narrowest measurement.

For height, you’ll need the tallest of the three measurements.

For outside mount Roman shades, start by measuring the width (outer edge of the trim from left to right). For windows without trim, add 2″ to 3″ on each side. Then, measure the height. For windows without trim, measure 2″ below and 3″ above. For windows with a protruding sill, start at the frame and extend 3″ above the top.  

How to Measure A Window for Plantation Shutters

Plantation shutters are wood or faux wood window treatments. To measure for inside mounted plantation shutters:

  1. Start by ensuring the squareness of the window. This is extremely important!
  2. Measure the window’s depth to make sure your new shutters will fit inside.
  3. Measure the window’s width in three places, using the narrowest measurement.
  4. Measure your window’s height in 3 places and use the shortest size of the three. 

Inside mounts only work on windows that are very near square. Determine squareness by measuring the window’s diagonal points. You can use a plumb bob (link to Amazon) for very accurately checking how perpendicular the outside edges are. If there’s more than a ¼” difference between the top and bottom or side to side, seriously consider outside mounting your new shutters. Out-of-square windows are not forgiving and your plantation shutters likely will not close properly.

To measure outside mounted plantation shutters, first, check to see if there’s a flat area to mount your hardware. These shades should not mount to the wall; it needs to be on the window frame. Get your measurements by determining the window’s width from trim to trim. Then determine the window’s height. 


Now that you have our guide to measuring for blinds, it’s time to get started! Get out your measuring tape, take notes of the measurements before you pick out your new shutters or blinds, and then enjoy your perfectly fitted window coverings!

This Post Has One Comment

  1. Afton Jackson

    I absolutely loved your guide on how to style blinds when mounted from the inside. With our new house fully furnished, we ended up noticing that the windows were a lot bigger than we expected and that we might need some coverings for them. Since we need to get blinds for all of them, I’ll use your guide to make sure we get accurate measurements before shopping for window coverings.

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