Curtain Size Calculator

Please fill in the required fields with values greater than 0.
–curtain rod width (in)
–total curtain width (in)
–finished curtain length (in)
–standard length to buy (in)

Estimate only. Standard ready-made curtains come in 63, 84, 95, 108 and 120 inch lengths. Hem or add a rod pocket if needed.

How to use this calculator

Measure the window width and height. Enter how far the rod extends beyond the window and how high above the window it sits. Choose the curtain length and fullness, then press Calculate to see the rod width, curtain width and length.

The formula

Rod width = window width + 2 × extension
Total curtain width = rod width × fullness
Curtain length = rod height above window + window height + drop to the sill, apron or floor

Example: A 48 in × 60 in window with a rod extending 4 in each side and 4 in above the window needs a 56 in rod and 112 in of curtain width (two 56 in panels) at 2x fullness. A floor length curtain is 93.5 in long, so buy 95 in curtains.

How to read your curtain size results

The curtain size calculator gives you three numbers: the rod width, the total curtain width and the curtain length to buy. The rod width tells you which rod to shop for. The total curtain width is the combined flat width of all panels, not the width of one panel. The length is what you match to the panel lengths sold in stores.

What changes the size

  • Rod extension. Extending the rod past the window lets open curtains stack on the wall instead of over the glass.
  • Rod height. Mounting the rod higher adds to the length and makes the window look taller.
  • Fullness. A 2x setting looks gathered and full. A 1.5x setting looks flatter and suits sheer or heavy fabrics.
  • Length style. Sill, below-sill and floor-length curtains each need a different drop.

Two examples

For a 48 by 60 inch window with a 4 inch extension on each side, the rod is 48 + 2 × 4 = 56 inches. At 2x fullness, you need 112 inches of total curtain width, such as two panels at least 56 inches wide each. The example on this page lands on a 95 inch curtain, a common stock length.

For a smaller 36 inch window with a 3 inch extension, the rod is 42 inches. At 2x fullness, you need 84 inches of curtain width, or two panels about 42 inches wide.

Tips and common mistakes

  • Measure each window. Windows in the same room are not always the same size.
  • Check how the panel hangs. Rings and clip rings add length, while rod pockets sit higher on the rod.
  • Do not buy panels that only cover the rod width. Flat curtains look skimpy when closed.
  • Allow for shrinkage if you plan to wash cotton or linen curtains.
  • Install the rod before you buy panels, then measure the real length from the rod to the floor.

Buying advice

If your calculated length falls between stock sizes, buy the next longer length and hem it, or raise the rod slightly. For wide windows, buy extra panels rather than stretching two across the gap. Choose a rod with a center support if it spans more than about 5 feet, so it does not sag.

Frequently asked questions

How wide should curtains be?
The total curtain width should be 1.5 to 2.5 times the rod width, so they look full when closed.
How high should I hang curtains?
Hang the rod 4 to 6 inches above the window, or closer to the ceiling to make the room feel taller.
How far should the rod extend past the window?
3 to 6 inches on each side lets the curtains clear the glass when open.
What curtain length should I choose?
Floor length curtains look best. Hang them about half an inch above the floor, or let them just touch it.
What are standard curtain lengths?
63, 84, 95, 108 and 120 inches.
How do you measure for curtains on a sliding glass door?
Measure the full width of the door frame, then add 4 to 8 inches on each side so the curtains can stack clear of the glass. For length, measure from the rod height to the floor. Most patio doors suit two wide panels or one large panel that slides fully to one side.
Should curtains be wider than the window?
Yes. The rod should extend past the frame, and the curtain fabric should be wider than the rod. Together, these let the curtains cover the window fully when closed and pull back off the glass when open. This also lets in more light and makes the window look larger.
How many curtain panels do I need for one window?
Divide the total curtain width from the calculator by the width of one panel, then round up. For example, 112 inches of total width with 54 inch panels needs about 2.07 panels, so buy 3 or choose wider panels. Most standard windows use two panels, one on each side.