Curtain Fabric Calculator
Flat Panels Look Skimpy — Fullness Is What Makes Curtains Read as Curtains
A curtain panel cut exactly to a window's width hangs flat and stingy once closed. Real fullness comes from using considerably more fabric than the window is wide — typically double to two-and-a-half times — so the closed curtain falls in soft folds rather than a stretched, flat sheet. That fullness ratio, not the window size alone, is what drives how much fabric actually needs to be purchased.
The Formula
Total Fabric Width Needed = Window Width × Fullness Ratio
Panel Count = ceil(Total Fabric Width Needed / Fabric Bolt Width)
Panel Length = Window Height + Hem Allowance
Total Fabric Length = Panel Length × Panel Count
Panel Count = ceil(Total Fabric Width Needed / Fabric Bolt Width)
Panel Length = Window Height + Hem Allowance
Total Fabric Length = Panel Length × Panel Count
Where This Calculation Matters
- Ordering the right yardage upfront — fabric dye lots vary between production runs, so calculating the full amount needed before cutting avoids a mismatched reorder later.
- Working within a bolt width — standard decorator fabric bolts commonly run 54 inches wide; when the total width needed exceeds that, multiple panels (seamed or separate) are required to achieve the desired fullness.
- Floor-length vs. sill-length curtains — window height plus hem allowance scales directly with how far the curtains are meant to hang, from a short cafe curtain to full floor-length drapery.
- Comparing fullness levels — a lower fullness ratio (around 2x) gives a more tailored, minimal look, while 2.5x or higher produces a fuller, more traditional drape — both change the fabric requirement directly.
Fabric Needed by Window Size
At the standard 2.0x fullness ratio, 12-inch hem allowance, and 54-inch fabric bolt width:
| Window size | Panels needed | Total fabric |
|---|---|---|
| 36 in × 60 in | 2 | 4.00 yards (3.66 m) |
| 48 in × 84 in | 2 | 5.33 yards (4.88 m) |
| 60 in × 96 in | 3 | 9.00 yards (8.23 m) |
How to Use This Calculator
- Enter Window Width and Window Height (in).
- Adjust Fullness Ratio if you want more or less gather than the 2.0–2.5x standard range.
- Adjust Hem Allowance if your project needs a different top and bottom hem total than the 12-inch default.
- Adjust Fabric Bolt Width to match the specific fabric you're purchasing (defaults to 54 in).
- Select Calculate to see the total fabric length in yards and meters, plus the number of panels needed.
Related Calculations
Coordinating curtain color with the room's palette? See the Room Color Scheme Calculator, or size a rug to match with the Rug Size Calculator.