About This Calculator
The key to great-looking curtains is fullness — the ratio of total fabric width to window width. Flat panels at 1:1 look skimpy; 2× fullness creates a classic gathered look; 2.5–3× is used for formal or luxurious drapes.
Fullness guide
- 1.5× (light): Minimal gather, modern/minimalist look
- 2× (standard): Classic look, works for most rooms
- 2.5–3× (full/luxe): Rich, formal drapes with deep folds
Hem allowance
Add 6–8 inches for a standard double-fold bottom hem and 2 inches for a top header. For floor-length drapes that puddle, add an extra 6–12 inches to your drop.
Frequently asked questions
How does this curtain calculator decide how many panels I need?
The curtain calculator multiplies your window width by the fullness ratio you pick (2× is the standard gathered look), then divides by the panel width to find how many panels give proper, even fullness.
What fullness should curtains have?
A 1.5× ratio looks light and flat, 2× is the standard gathered look, and 2.5–3× gives a luxurious full drape. Sheer fabrics usually look best at higher fullness.
How much fabric do I need to sew my own curtains?
The tool estimates yardage from your drop height plus hem allowance, multiplied by the number of panels. Add extra if your fabric has a pattern repeat that needs matching.