Curtain Width Calculator
Enter your window width, how far the rod extends and the fullness you want to see the rod width, total fabric width and width of each panel.
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How to use the Curtain Width Calculator
- Type your window width into the window width box, in in, ft, cm or m.
- Decide where the rod will go and how far it will stick out past each side of the window.
- Under more options, enter “Rod beyond each side of the window”. It starts at 6 in.
- Read the rod width. It equals the window width plus both extensions.
- Set “Fullness (× rod width)”. It starts at 2. The total fabric width is the rod width multiplied by fullness.
- Set the number of panels. It starts at 2. The width of each panel is the total fabric width divided by the number of panels.
- Under more options, check the width of one ready-made panel. It starts at 50 in. Then read “Ready-made panels needed”, which is the total fabric width divided by the panel width, rounded up.
- For ready-made panels, read the package width, width first then length, and enter it as the panel width.
Four presets are available: a 36 in window, a 48 in window, a 72 in window with fullness 2.5, and a 36 in window with one panel. The page shows a warning if fullness is outside 1.5 to 3, the window width is outside 12 to 240 in, or a panel would need to be wider than 120 in. It shows an error if the window width is missing or not above zero, an extension is negative, the panel count is not a whole number from 1 to 20, or the panel width is zero.
How is curtain width calculated?
Curtain width is calculated in four steps: rod width, total fabric width, width of each panel, and the number of ready-made panels. Each step uses the result of the one before it. Rod width is the window width plus two times the rod extension. Total fabric width is the rod width times fullness, and each panel is the total divided by the number of panels.
With the default values of a 48 in window, 6 in on each side and fullness 2, the rod width is 60 in (152.4 cm) and the total fabric width is 120 in (304.8 cm). Two panels give 60 in each. For ready-made 50 in panels, 120 ÷ 50 = 2.4, which rounds up to 3 panels.
How far should a curtain rod extend past the window?
Guides give different extensions past each side of the window: 4 to 6 in, 6 to 12 in, at least 6 in, or 8 to 12 in. The page starts at 6 in and lets you set any value. A second chart in the guides places the rod 3 to 12 in above the window, depending on the guide. A larger extension makes the rod width and total fabric width greater.
What fullness should I use for curtains?
Fullness is the multiplier that turns rod width into fabric width. The guides suggest 1.5 to 3 times, with 2 times listed as the most common. Individual guides give 1.5 to 2, 2, 2 to 2.5, or 2 to 3. The page starts at 2 and shows a warning outside 1.5 to 3. A higher fullness uses more fabric and gives more gathers.
How wide is a ready-made curtain panel?
Guides list 48 in, 48 to 54 in, or 50 to 54 in for one ready-made panel. Sizes vary by maker, so check the package. The page starts at 50 in, and you can change it to match your panels. The panel width on a package is the flat width before gathering. The calculator uses the number you enter, so it does not tell you which panel size is right for your room.
Sources (checked 15 October 2026): amandakatherine.com · excitingwindows.com · linenchest.com · blog.kwikhang.com · engineerfix.com · dgfloors.com
Worked examples
| Input | Result |
|---|---|
| window 48 in, fullness 2, 2 panel(s) | rod 60 in, total fabric 120 in, 60 in per panel |
| window 72 in, fullness 2.5, 2 panel(s) | rod 84 in, total fabric 210 in, 105 in per panel |
| window 36 in, fullness 1.5, 1 panel(s) | rod 48 in, total fabric 72 in, 72 in per panel |
| window 1.5 m, fullness 2, 2 panel(s) | rod 70.9 in, total fabric 141.7 in, 70.9 in per panel |
Calculated by the tool above; open it with the same values to see each step.
Frequently asked questions
What is a standard curtain width?
Typical ready-made panel widths in the named guides range from 48 in to 54 in. Sizes vary by maker, so use the width printed on your package. The calculator starts at 50 in.
How do I measure curtain width?
Measure your window width, add the rod extension to each side, then multiply by fullness. Divide that total by the number of panels to get each panel’s width.
Does the calculator confirm my curtains meet a standard?
No. It only calculates widths from the numbers you enter. It does not check your curtains against any code or rule.
Can I enter measurements in centimetres?
Yes. You can type widths in in, ft, cm or m.
Why does the ready-made panel count round up?
The number of ready-made panels is the total fabric width divided by the panel width, rounded up. For example, 132 ÷ 48 = 2.75, which gives 3 panels.
What does the warning about fullness mean?
The page shows a warning when fullness is outside 1.5 to 3. The calculation still runs, but the value is outside the range the page uses.
How far should the rod stick out past the window?
The calculator starts at 6 in beyond each side of the window. You can change it under more options. The rod width is the window width plus both extensions, and the total fabric width is the rod width multiplied by fullness.
Related tools
- Curtain Size Calculator: Use it when you want to work out curtain size beyond width alone.
- Curtain Length Guide: Read this when you need to choose a curtain length.
- Curtain Length for 8 Foot Ceilings: Check this if your ceiling is 8 feet high.
- Curtain Length for 9 Foot Ceilings: Check this if your ceiling is 9 feet high.
- Standard Shower Curtain Width and Size Chart: Use this for shower curtains rather than window curtains.