Curtain Sizing Guide: Measure Your Windows Like a Pro

Getting curtains that look right starts with a good measurement. Too short and they look cheap, too wide and they block light. Follow these simple steps and you’ll pick curtains that fit your space without a second guess.

Step‑by‑Step Width Measurement

First, decide if you want an inside mount (inside the window frame) or an outside mount (covering the frame). For an inside mount, measure the exact width of the frame from one side to the other. Use a steel tape and write down the number in inches or centimeters.

Next, add extra width for a nice look. Most designers suggest the curtain fabric be 1.5 to 3 times the window width. If your window is 48 inches wide, aim for a total curtain width of 72‑96 inches. This extra width gives a soft fold when the curtains are closed.

When you buy a ready‑made set, check the product listing for the total width of the pair. If you’re ordering custom curtains, give the fabric supplier both the exact frame width and the desired fullness factor (1.5‑3×). This way they’ll cut the right amount of material.

Step‑by‑Step Length Measurement

Length depends on where you want the curtains to end. Common options are ‘sill length’ (just touching the window sill), ‘below sill’ (a few inches lower), or ‘floor length’ (slightly touching or grazing the floor). Measure from the point where the rod will sit down to the desired end point.

If you’re using an inside mount, measure from the top of the window frame to the sill or floor. For an outside mount, measure from the top of the rod (usually a few inches above the frame) down to the same end point. Add a little extra—about 2‑4 inches—if you want a small puddle on the floor for a luxe look.

Don’t forget to check the length of the rod itself. Some rods have brackets that raise the curtain a bit, so factor that into your measurement. When in doubt, measure twice and write down the numbers before you order.

Here are a few quick tips to avoid common mistakes:

  • Use a metal tape, not a cloth one—cloth stretches and gives a wrong reading.
  • Measure at least twice, once in each direction, to catch any uneven windows.
  • If you have a bay window, treat each pane separately or measure the total opening.
  • Consider the curtain heading type (pleated, grommet, rod pocket) because it adds a few extra inches.
  • When ordering online, read the size guide carefully; some sellers list width per panel, not total width.

Once you have the right numbers, you’ll find more confidence picking styles that match your décor. Whether you go for a light cotton for a breezy look or a heavy velvet for drama, the correct size makes all the difference.

Remember, measuring isn’t a science experiment—just a practical step to keep your windows looking polished. Grab your tape, follow the steps, and you’ll have curtains that fit like they were made for your home.