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Curtain size calculator
Enter your window dimensions and ceiling height. Get rod length, panel count, panel width, and standard length — with the rationale behind each number.
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<iframe src="https://plopit.app/tools/curtain-size-calculator?embed=1" width="100%" height="900" frameborder="0" title="Curtain size calculator by PlopIt"></iframe>How the calculator decides
Rod length is the window width plus roughly 14 inches (7 inches each side) so the curtains stack at the edges when open and expose the entire window. For inside-frame mounts, no extension is added.
Total fabric width is the rod length multiplied by the chosen fullness. 2× is the standard; denser fullness produces deeper folds. The calculator divides total fabric width by 50 inches (standard panel width) to compute the panel count.
Panel length depends on the mount height plus the chosen length style. Kiss-the-floor is the safest default. The result rounds up to the nearest standard length (63, 84, 96, 108, 120, or 132 inches). If the required length exceeds 132 inches, custom panels are needed.
Standard panel lengths
| Length | Best for | Ceiling height |
|---|---|---|
| 63" | Apron-length on standard window | Any |
| 84" | Floor-length on lower windows | 8 ft |
| 96" | Floor-length, standard mount | 8 ft (safest default) |
| 108" | Floor-length, ceiling mount | 9 ft |
| 120" | Floor-length, ceiling mount | 10 ft |
| 132" | Tall rooms, puddle finish | 11+ ft |
Frequently asked questions
How many curtain panels do I need for one window?
For a standard window, two panels at 2× fullness is the default — each panel approximately 50 inches wide. Wider windows or higher fullness (2.5× or 3×) push the count to three or four. Single-panel installations work only for narrow windows under 24 inches wide.
What is curtain fullness?
Fullness is the ratio of total fabric width to rod length. 1.5× gives a flat, modern look (lower fabric volume). 2× is the standard for most rooms. 2.5× to 3× is for formal rooms with heavy fabrics or sheer panels where extra volume reads as luxurious.
What is the right curtain length?
Floor-length is the default for living rooms and bedrooms — specifically 'kiss the floor' (just touches) for the cleanest read. 'Float' (0.5 inch above) is high-traffic-friendly. 'Puddle' (4-8 inches pooled) is for formal rooms. Sill or apron length is for kitchens or above-radiator windows only.
How high should I hang the curtain rod?
Above-frame mounting at 4-12 inches above the window frame is the standard. Ceiling mounting (just below the ceiling) maximizes vertical drama and works well with 9+ foot ceilings. Inside-frame mounting works for cafe-style or minimalist setups.
How wide should the curtain rod be?
The rod should extend 6-8 inches past each side of the window frame. This gives the curtains somewhere to stack when fully open, exposes the entire window for maximum light, and makes the window appear wider than it actually is.
What is the most common curtain mistake?
'Flood-pants' curtain length — buying 84-inch panels for an 8-foot ceiling, leaving the curtains ending 4-12 inches above the floor. The fix is sizing up to 96-inch standard panels or mounting the rod closer to the window frame instead of higher up.