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How to Measure Windows for Curtains

The addition of curtains can make a big difference for any window, but figuring out the size of the curtains you need is easier said than done. Measuring windows for curtains can be a little tricky, so here are some guidelines to help you make the perfect measurements.

What Tools Do You Need?

Preparing to install curtains requires a number of tools, both for measuring the window size and for installing the curtains. You’ll want to have the following tools on hand:

For measuring:

  • Pencil and paper
  • Metal measuring tape

For installing curtains:

  • Electric drill
  • Screwdriver
  • Screws
  • Brackets to hang rod
  • Step ladder
  • Rod hardware


Where to Mount the Hardware

Knowing where you’re going to mount the curtain hardware is the first step to making accurate measurements. Will it be mounted inside the window frame, so that the curtains span the window and nothing more, or will you be mounting on the wall outside the window frame? There are advantages and disadvantages to each; inside-mounted curtains place a great emphasis on the window itself, while outside-mounted curtains are ideal if the window frame isn’t perfectly square.

inside mount

For an outside mount, the drapery rod placement can vary.

Generally, it should be installed 3 to 4 inches above the top of the window frame. However, installing the drapery rod farther above the window can be useful for making a small room look bigger.

make small room look bigger


How to Measure Width

measure window width


When measuring the width of your window, it’s important not to take just one measurement and assume it’s correct. In many cases, window frame width is not level from the top to the bottom. As a result, you should take three measurements (one at the top, one in the middle, and one at the bottom) to get a more accurate number. If you’re measuring the inside of the frame, choose the shortest (narrowest) measurement; if you’re measuring the outside of the frame, choose the longest (widest) measurement.

Also, don’t assume that you should purchase just enough curtain material to span the width of the window. To give “fullness” to your curtains, you’ll want to use substantially more material than you might expect. Decide if you want a full or very full appearance.  Take your width measurement (let’s say 40 inches) and either double it or triple it (for a very full look), meaning that you would purchase 80 inches or 120 inches of total panel material for the curtains.


How to Measure the Length

There are several ways to measure the length of the window as well, depending on how low you want the curtains to extend. Options include measuring from the drapery rod to the window sill, to a little below the sill, or all the way to the floor. When measuring to the floor, you can also add a few inches to your measurement to allow the bottom of the curtains to drape on the floor. This is called “puddling” and can range from just an inch or two of extra material to a full foot of material trailing on the floor.

measure window to sill

measure just below sill

measure window to floor

measure window for puddling

In addition, the type of hardware that you use can affect how you make your measurements. If you will be using drapery rings on the rod, their size will determine how far the curtains hang from the rod. You want to measure from the rings rather than the rod itself.

To help confirm that your measurements are correct, you should measure the length in three places (down the left side, down the middle, and down the right side), just as you did when measuring the width, this time using the longest length.

measure window length


How Long the Drapery Rod Should Be

If you’re mounting the drapery rod outside of your window frame, you’ll likely want to add a few inches to the measurement of the window frame so that the drapery rod spans the window width, with room to spare on each side. Also, if your drapery rod will have finials on the ends, be sure to factor in their length as well to make sure that there will be room on your wall for the rod and the finials.

measure for finial length


By keeping these steps in mind, you should be well on your way to achieving perfect measurements for your curtains.

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