Utility
Curtain Calculator
Calculate curtain width, length, rod size, and total fabric needed based on your window measurements and style preferences.
Enter window dimensions and click Calculate
How is this calculated?
Outside Mount:
Rod Width = Window Width + 12" (6" each side)
Curtain Length = Window Height + 4" (above) + distance to floor
Inside Mount:
Rod Width = Window Width - 0.5" (clearance)
Curtain Length = Window Height - 0.5"
Total Curtain Width = Rod Width × Fullness Factor
Width Per Panel = Total Width ÷ Number of Panels
Fabric per panel:
Cut length = Curtain Length + 4" (header) + 8" (hem)
Cut width = Panel Width + 4" (side hems)
Total fabric = Cut length × Cut width × Panels
Standard fullness factors:
1.5× = flat/minimal, good for thick fabrics
2.0× = standard, works for most fabrics
2.5× = full/rich, best for sheers/light fabricsFAQ
Frequently asked questions about curtain sizing
How wide should curtains be?
Curtains should be 1.5× to 3× the window width for proper fullness. Standard fullness is 2× (a 60-inch window needs 120 inches total curtain width). Sheer curtains look best at 2.5-3×, while heavier fabrics work at 1.5-2×.
How long should curtains be?
Floor-length curtains should end 0.5 inches above the floor. For a 'puddle' look, add 2-6 inches. Sill-length curtains end 0.5 inches above the sill. Apron-length extends 4 inches below the sill. Always measure from the rod, not the window top.
What's the difference between inside and outside mount?
Inside mount fits within the window frame (cleaner look, shows trim). Outside mount hangs outside the frame and should extend 3-6 inches beyond each side and 4-6 inches above. Outside mount makes windows appear larger.
How wide should a curtain rod be?
The rod should extend 3-6 inches beyond each side of the window frame for an outside mount. For a standard 36-inch window: rod = 36 + 6 + 6 = 48 inches. This allows curtains to stack off the glass when open, maximizing light.
How many curtain panels do I need?
For most windows, 2 panels (one each side) is standard. Wide windows (over 60 inches) may need 4 panels for adequate fullness. Single panel works for narrow windows or asymmetric looks. Each panel should be half the total required width.
How much fabric do I need for custom curtains?
Per panel: Length + header allowance (4 in) + hem allowance (8 in) + pattern repeat. For width: panel width + 4 inches for side hems. Multiply by number of panels. Add 10% for shrinkage if the fabric isn't pre-shrunk.