Curtain Size Calculator
Asking yourself what size curtains do I need for a window? Enter your window's width and height below and this free calculator gives you the recommended curtain rod length, how wide each panel should be, and how long the panels should hang — instantly, with no sign-up.
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Enter your window size to see what size curtains you need.
How to use this calculator
Measure your window width and height in inches — width from frame edge to frame edge, and height from the top of the frame down to the sill. A tape measure and thirty seconds are all you need.
Choose where the curtains will end: inside the frame at the sill, above the sill for a short curtain, or floor length for full-length panels. Then set the fullness factor — 1.5 gives the standard gathered look most people want, while 2 gives a fuller, more gathered drape. Results update instantly as you type.
How it works
The recommended rod width is the window width times the fullness factor: rod width = window width × fullness. The 1.5× minimum is a rule of thumb so the closed panels fully cover the glass and stack off to the sides when open, which also makes the window look bigger. This calculator rounds the rod width to the nearest inch.
Panels are split in two by default, one per side: each panel width = rod width ÷ 2, rounded to the nearest inch. So a 90-inch rod needs two 45-inch-wide panels.
Panel length follows these standard rules of thumb, based on where the curtain ends: above-sill = window height + 4 in; sill = window height + 6 in; floor = window height + 10 in. Floor-length panels should just skim or kiss the floor. For example, a 60-inch-wide window with a fullness of 1.5 gives a 90-inch rod and two 45-inch panels; an 80-inch-tall window hung floor-length needs 90-inch panels.
These are rules of thumb, not exact measurements. Curtain packages come in standard sizes, so round up to the nearest available panel size and always re-measure before you buy — rod placement and header style (rod pocket, grommets, rings) shift the finished length by an inch or two.
Frequently asked questions
What size curtains do I need for a 60-inch window?
For a 60-inch-wide window, use a curtain rod about 90 inches long — 1.5 times the window width. Hang two panels, each about 45 inches wide, so they gather nicely when closed and stack off the glass when open. Panel length depends on where you want them to end: add 4 inches to the window height for above-sill curtains, 6 inches for sill-length curtains, or 10 inches for floor-length curtains.
How wide should a curtain rod be compared to the window?
A curtain rod should be 1.5 to 2 times the window width. The extra width lets the panels stack to the sides without covering the glass, which makes the window look bigger and lets in more light. This calculator uses 1.5 times the window width as the recommended default, and you can raise the fullness factor to 2 for a fuller, more gathered look.
How long should curtains be — above the sill, to the sill, or to the floor?
It depends on the look you want. As a rule of thumb, above-sill curtains run about 4 inches past the window height, sill-length curtains about 6 inches, and floor-length curtains about 10 inches past the window height. Floor-length panels should just skim or kiss the floor; curtains that stop mid-wall between the sill and the floor tend to look unintentionally short.
Should curtains be wider than the window?
Yes. For a gathered, finished look, the total curtain width should be 1.5 to 2 times the window width. Anything less looks flat and skimpy, especially with lightweight fabrics. With two panels, each panel should be half of the total — so a 90-inch rod needs two 45-inch panels.
One panel or two — how many curtain panels do I need?
Most standard windows look best with two panels, one on each side, because they frame the window symmetrically and stack neatly when open. A single panel works for narrow windows or an asymmetric, modern look — just make sure a single panel is still 1.5 times the window width so it covers the glass when closed.