Curtain Fabric Calculator
Panels, cut length, and total cloth for gathered curtains.
What it does
Curtains need more fabric than the window measures. Folds eat width, hems eat length, and panels come only in whole cuts. Guessing at the store ends with short panels or flat looking gathers.
The tool above does the yardage in order. It multiplies span by fullness, divides by fabric width and rounds up to whole panels, then adds hem allowance to the drop. You read panels, length each, and total to buy.
Extension sewing guides teach the same sequence: full width first, then cut length with hems and headers. Fullness near 2 suits most cottons; sheers want more, heavy drapes want less. The 10 inch imperial and 0.25 m metric allowances cover a standard hem plus header.
Measure the closed span, not the glass alone, when blackout or privacy matters. Outside mount gear needs the trim covered. With panels and total length in hand, add pattern repeat only if the print demands it.
How to use
- Pick imperial (inches) or metric (meters).
- Measure the span the closed curtains must cover.
- Enter drop from rod to planned hem.
- Pick fullness: 1.5 flat, 2.0 standard, 2.5 full.
- Enter fabric width off the bolt.
- Buy the panel count times the per panel length.
Formula
- window
- Span to cover when closed, in meters or inches.
- drop
- Finished drop from rod to hem, plus hem allowance.
- fabric width
- Fabric width off the bolt.
- fullness
- Gather multiplier from 1 to 3.
Hems add 0.25 m per panel in metric and 10 in per panel in imperial. Fullness is a multiplier: 1.5 for flat panels, 2.0 for standard gather, 2.5 for lush folds. Always round panels up; a partial panel still needs full length.
Worked example
Example: 71 inch window
71 inch window, 87 inch drop, fullness 2.0, 55 inch fabric.
- Window is 71 in, fabric is 55 in, fullness 2.0.
- Needed width: 71 x 2 = 142 in.
- Panels: 142 / 55 = 2.58, round up to 3.
- Length each: 87 + 10 hems = 97 in.
- Total: 3 x 97 = 291 in of fabric.
Reference table
| Fabric | Fullness | Look |
|---|---|---|
| Sheer voile | 2.5 to 3.0 | Soft, airy gather |
| Light cotton | 2.0 to 2.5 | Classic fold |
| Medium drape | 2.0 | Standard cover |
| Heavy velvet | 1.5 to 2.0 | Deep, weighty fold |
| Flat panel | 1.0 to 1.5 | Minimal gather |
Limits
- Straight panels only. Pleat styles with buckram need shop cutting plans.
- Pattern repeat needs extra beyond this math.
- Rod pockets versus grommets shift header use slightly.
- Stretch and shrinkage vary by fiber and wash.
Common mistakes
- Measuring glass instead of cover span.
- Skipping fullness and hanging flat sheets.
- Forgetting hems, then coming up short.
- Rounding panels down to save cloth.
- Ignoring pattern repeat on large prints.
Try it yourself
Quick checks. Answers sit tucked under each question.
Fabric for 2.4 m span, 2.5 m drop, fullness 2, 1.4 m cloth?
Need is 4.8 m. Panels are ceil(4.8 / 1.4) = 4. Each is 2.75 m. Total is 11.00 m.
Fabric for 95 in span, 98 in drop, fullness 2, 55 in cloth?
Need is 190 in. Panels are ceil(190 / 55) = 4. Each is 108 in. Total is 432 in.
Questions
How is curtain yardage figured?
Needed width is window times fullness. Panels are that width divided by fabric width, rounded up. Length each is drop plus hems. Total is panels times length each.
What fullness should I pick?
Thin sheers gather near 2.5 to 3, medium cotton near 2, heavy velvet near 1.5. More fullness gives deeper folds and better cover when closed.
How much extra for hems and headers?
Add about 10 inches total in imperial (4 hem plus 6 header) or 0.25 m in metric. Wide or heavy drapes may want deeper hems to hang straight.
Do patterned fabrics need extra?
Yes if the print has a large repeat. Add one full repeat per panel beyond the plain length. Small prints and solids need no match allowance.
Should I measure the glass or the whole trim?
Inside mount covers the glass; outside mount covers trim for better blackout. Measure the span the curtains must cover when closed, not just the glass.
How do I convert inches to yards at the store?
Divide total inches by 36 for yards before buying. Here 291 in / 36 = 8.08 yd, so buy 8.25 to 8.5 yd depending on cut policy.
Sources
- Iowa State Extension: sewing and home textiles
- Cornell Cooperative Extension resources
- NIST: weights and measures