We Wrote Your Complete Guide to Measuring Windows for Curtains

A dining room flanked by a set of glass doors, which have been framed with white curtains

Pure Salt Interiors

Of all the decorative touches you add to a room, curtains may be one of the most important—think of them as an ornate picture frame, with the view outside your window being the art. Though their style is certainly important, curtains are also functional, controlling how much natural light enters your room, and helping regulate temperature and airflow. And if curtains are going to make your room look good and do their job properly, they need to fit perfectly, which is why you should always measure your windows before purchasing window treatments. Here’s how to do it. 

What You Need

Before you measure for curtains and drapes, make sure you have the right tools and resources to make the process as simple as possible. This will ensure your measurements are accurate and efficient. Here are the items you should have on hand before you measure your windows for curtains:

  • Measuring tape
  • Step stool (and, preferably, someone to spot you for safety)
  • Pencil with eraser
  • Masking tape

Step One: Install and Measure Your Curtain Rod

If you don’t already have an existing curtain rod, you’ll first need to decide where to mount one, and what hardware you’ll need to do the job. Curtain rods are held up with brackets that can be simple enough to practically disappear, or can be ornate and decorative. 

Most rod-and-bracket sets are sold with detailed mounting instructions, and make sure you don’t accidentally throw them out! Improperly installed brackets can rip out of a wall under the weight of heavy window treatments, like drapes, and may require additional mounting hardware, like wall anchors.

The style of your curtains will inform how high you hang your rod. For example, valances and tag-top curtains are usually hung at least eight inches above the top edge of the window frame, while simple shades and rod-pocket curtains can be hung as low as four inches. 

To create the illusion of high ceilings, install your curtain rod just below where the wall meets the ceiling. 

Use your measuring tape and a pencil to mark where you’ll be installing the brackets; if you’d rather not write directly on your walls, use a piece of masking tape. Hold your curtain rod flat against the wall between them, and use a level to make sure it will be straight before you begin drilling holes into your wall. (Once hung, use your level to check it again, just in case.)

After the brackets are installed, adjust the width of the curtain rod so that it extends past the sides of the window, so the curtains have room to gather when open. For light window treatments, leave an overhang of at least six inches on either side; for bulkier curtains and drapes, 12 inches.

Step Two: Calculate the Curtain Width

Once hung, measure the curtain rod end-to-end with metal measuring tape; if the rod has decorative finials on each end, do not include them in the measurement. Next, multiply this number by two; since curtains gather, you’ll need ones that are at least twice as wide as your window. Multiply by three if your curtains are wispy or sheer, or if you’d like your curtains to have a fuller, more dramatic appearance.

Curtain panels are usually sold as single panels—not pairs—so before purchasing, check if the curtains you’ve chosen come in a set of two, or if you’ll need to buy multiple panels to cover your window. Most ready-to-hang curtain panels come in three widths: 44 inches, 66 inches, or 90 inches.

Step Three: Measure the Curtain Length

Once you’ve calculated your width measurement, decide if you’d like your curtains to fall to the windowsill, the floor, or somewhere in between. Mark the spot with pencil or masking tape. Measure the distance from the curtain rod to the marking.

Ready-to-hang curtains usually come in three lengths: 84 inches, 96 inches, or 108 inches. Purchase panels that are longer than your desired length; and hem them with safety pins, iron-on hemming tape, or a sewing machine.