Have you ever hung curtains that looked flat and skimpy on the rod? The gap is usually fabric width, not height. The Curtain Size Calculator turns your window size into panel width, panel length, and rod width.
It is made for homeowners and renters shopping for ready-made panels. You enter the window frame size, pick a fullness ratio, and choose a hanging style. The numbers update when you press the button.
Table of Contents
- What the Calculator Does
- How to Use It, Step by Step
- The Curtain Size Formula
- Worked Example
- How to Read the Results
- Fullness and Length Style Tips
- Limitations and Assumptions
- FAQs About the Curtain Size Calculator
What the Calculator Does
The tool works from the window frame size in inches. Four inputs feed three clear results.
- Panel Width (Each of 2 Panels): the finished width to look for per panel, in inches.
- Recommended Panel Length: the nearest standard off-the-shelf length, such as 63, 84, 95, 108, or 120 inches.
- Curtain Rod Width: how wide to set the rod, which is the window width plus 6 inches on each side.
It assumes a two-panel setup, one panel for each side of the window.
How to Use It, Step by Step
- Enter Window Frame Width (Inches). The sample value is 60 inches.
- Enter Window Frame Height (Inches). The sample value is 72 inches.
- Pick a Curtain Fullness Ratio. The choices are 2.0x, 2.5x, and 1.5x.
- Pick a Hanging Length Style. The choices are apron, floor, and puddle.
- Press Calculate Curtain Panel Sizes to see the three results.
The Curtain Size Formula
The tool widens the rod past the glass, then multiplies by the fullness ratio. That total fabric width is split across two panels.
Window Width + 12×Fullness÷2 Panels=Panel Width
- Rod width = window width + 12 inches (6 inches past each side).
- Total fabric width = rod width times the fullness ratio.
- Panel width = total fabric width divided by 2, rounded up to a whole inch.
- Drop = window height plus 4 inches for apron, 12 inches for floor, or 15 inches for puddle.
- Panel length = that drop rounded up to the next standard length.
Worked Example
Priya has a bedroom window that is 48 inches wide and 60 inches tall. She wants deluxe folds and floor-length panels. She picks 2.5x fullness and the floor style.
| Result | Calculation | Output |
|---|
| Rod Width | 48 + 12 | 60 inches |
| Total Fabric Width | 60 times 2.5 | 150 inches |
| Panel Width | 150 divided by 2 | 75 inches each |
| Drop | 60 + 12 | 72 inches |
| Panel Length | 72 rounded up | 84 inches |
So Priya buys two 75 inch wide panels in the 84 inch length. She sets her rod 60 inches wide.
How to Read the Results
Panel Width is the finished width per panel, not the pair. Two panels of this width give the gathered look at your chosen fullness.
Recommended Panel Length rounds up to a size stores actually stock. A longer panel can be hemmed, but a short one cannot grow.
Curtain Rod Width tells you how wide to mount the hardware. The extra width lets open panels clear the glass for more daylight.
Fullness and Length Style Tips
Fullness controls how rich the folds look. The 1.5x ratio gives a flat, tailored look, while 2.5x gives deep gathers. Sheer and light fabrics often use higher fullness.
The length style sets the drop. Apron stops a few inches below the sill, floor just kisses the floor, and puddle pools fabric on the ground. If you want to size the glass itself first, the window area calculator helps.
Curtains are one layer of a room refresh. Pair them with the wallpaper estimator or size feature walls with the wall area calculator. For patterned fabric or paper, the wallpaper roll calculator plans repeats. Browse more in the home and construction calculators hub.
Limitations and Assumptions
- The tool uses inches only. It does not offer a metric option or fabric yardage.
- It assumes two panels and a rod set 6 inches past each side of the frame.
- The length rounds to common stock sizes up to 120 inches. If the drop is over 120 inches, the tool flags a custom length.
- A blank, zero, negative, or below-12-inch width or height shows a message and clears the results. It no longer falls back to the sample values.
- The drop adds a fixed allowance per style and does not account for heading tape or deep hems.
FAQs About the Curtain Size Calculator
Why is the panel wider than my window?
Curtains need extra fabric to form folds when closed. The tool multiplies the rod width by your fullness ratio to get that gathered look.
Does the width shown cover both panels?
No. The width is for one panel. You buy two panels of that width, one for each side.
What fullness ratio should I choose?
Use 1.5x for a flat, tailored style and 2.0x for everyday folds. Pick 2.5x for sheers or a deluxe, gathered drape.
How far past the window should the rod go?
The tool extends the rod 6 inches past each side. This lets open panels stack off the glass and let in more light.
Why does the length jump to a set number?
Ready-made panels come in fixed lengths like 84 or 95 inches. The tool rounds your drop up to the next stock size.
Can I use this for very tall windows?
The length tops out at 120 inches. Taller windows or high-mounted rods usually need custom-made panels.
This calculator gives planning estimates only and is not professional engineering, electrical, or building code advice. Reviewed for general accuracy by Prof. Dr. Khalil Mudassar, PhD.