As capable as they are of revamping a space, curtains can’t fully live up to their potential unless they’re properly measured. A couple inches too shy of an accurate measurement could find you face-to-face with drapes that are the equivalent of awkwardly short pants. Fortunately, Haley Weidenbaum, founder of Everhem, clued us in on how to measure curtains properly—it’s the same for velvet styles, sheers, and blackouts!—and advised us on how to do it right the first time. 

Inside Mounts vs. Outside Mounts

bed with open patio window
Photography by Yoshihiro Makino; Styling by Kate Berry

Inside Mounts

When you install your curtain rod inside the window frame, it’s called an inside mount. 

The pros: This method allows more light in because the panels don’t provide coverage between the wall and the edge of the windows. Additionally, if you want to show off decorative window trim, inside mounts allow it to remain visible. 


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The cons: Too much light could make the room uncomfortably bright. Sunlight can also fade some fabrics (including the curtains themselves), furniture, and flooring.

Outside Mounts

This more popular mounting style involves installing the rod on the wall, a few inches outside and above the window frame.

The pros: If you mount the rod wider than the frame, the window will appear bigger—a win for cramped spaces.

The cons: More coverage contributes to a darker room. 


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Common Mistakes People Make When Measuring for Curtains 

white living room with armchairs white curtains
Photography by Cody Guilfoyle

Only Taking One Measurement

Don’t allow the anticipation of seeing your newly transformed room to pressure you into rushing through the process. If you rely on measuring just once, it’s more likely to lead to a major curtain-hanging fail. Weidenbaum recommends taking three separate measurements to ensure accuracy. 

Not Knowing About Stack

Designers use the term stack to reference the amount of space curtains take up when they’re fully open. You’ll need to take separate measurements of the wall space you want to cover (if any) on the left and right of the window to account for it. Weidenbaum recommends leaving at least 8 inches of stack on each side, 12 for larger windows. “In other words, your rod will extend past your window on the left 8 inches and 8 inches on the right,” she explains. “You want the fabric to live on the sides and not eat into the glass.”  

Not Considering the Length Hardware Adds

“If you’re buying hardware from one place and panels from another, keep in mind the drop that the drapery ring will create,” says Weidenbaum. If the rings are 2 inches tall, for example, you’ll need to adjust your mount height to accommodate them.

How to Measure Curtains

green sofa living room with black curtains
Photography by Brittany Ambridge

The Supplies

  • A sturdy tape measure that is at least 16 feet long (anything smaller will be too flimsy and can’t handle lengthier curtains)
  • Your phone (or a pen and paper)
  • A friend to record dimensions while you measure 
  • Step stool or ladder, depending on window height

Step 1: Measure the Window Width

Weidenbaum recommends taking three different measurements—one across the top of the window, one across the middle, and the last across the bottom; keep track with your pen and paper or Notes app on your phone. Be sure to measure from the edge of the trim, aka the outermost part of the window. In addition to helping you catch any unintentional human errors (sometimes those sixes magically turn into nines), Weidenbaum says this method will bring to light any infrastructure issues. “A lot of windows aren’t straight,” she explains. “So you could get a different reading at each of those three points.” In that case, go with the longest length you recorded. 


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Step 2: Measure the Stacks 

In addition to planning for an 8-inch allowance on either side of the window, Weidenbaum suggests taking the same approach for above the frame; an 8-inch (or more) top stack can help elongate your space.

Step 3: Measure From the Floor to the Top of the Window 

Again, Weidenbaum recommends writing down three measurements—this time, vertical ones from the left side of the window, down the middle, and then the right side—for accuracy’s sake. 

Step 4: Measure the Mount Height

Mount height refers to the space between the top of the window molding and where you plan to mount the rod. Weidenbaum recommends one of at least 3.5 inches, especially if you’re decorating a spot with lower ceilings. “When you mount higher above the window, it makes the window and the room look bigger,” she explains. “The goal is that you don’t want the curtain rod to touch the ceiling and you don’t want it to touch the window. You want it to land halfway between.” 

Step 5: Decide How Long You Want Your Curtains to Be

Standard curtain lengths are 63 inches, 84 inches, 96 inches, and 108 inches. Depending on your window size, floor-length ones fall somewhere between 84 and 96 inches, which you’ll get to with your step 3 measurement. However, “some people like a puddle where the curtains hang longer,” says Weidenbaum. ”So if that’s what you want, you need to add 3 to 6 inches to the total height measurement.”


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Step 6: Add All Your Numbers Up 

Start by calculating the total width: Add up the inches for the stacks on the left and right with the width of the window. Then do the total height: Add the mount height plus the height from the floor to the top of the window plus your puddle. Write both down on your notepad or put in your phone to bring with you to the store. You are all set to transform your space, beginning with a curtain makeover!