Curtain Size Calculator — Fabric Width & Drop
Work out exactly how much fabric to buy for your curtains. Enter the window width and height, choose your heading style, and get the cut width and drop for each panel plus the total fabric area.
cm
cm
Curtain heading style
cm
cm
cm
Includes 10 cm header allowance + 15 cm bottom hem allowance
- 1
Track width (window + overhang)
150 + 2 × 15 = 180 cm - 2
Finished drop
220 + 15 − 1 = 234 cm - 3
Cut length per panel
234 + 10 + 15 = 259 cmAdds 10 cm header allowance and 15 cm double bottom hem.
How does this calculator work?
To size curtains, multiply the total pole width by the fullness factor (1.5–3× depending on heading style) to get fabric width, then divide by the number of panels and add side hems. Cut length equals window drop plus header and bottom hem allowances. This gives the exact cut dimensions per panel before sewing.
Formula
How this is calculated
Curtain fabric requirements depend on three things: how wide the coverage needs to be, how long each panel hangs, and how full the gathering or pleating is. The width starts from the window glass, extends by a rod overhang on each side (so the curtain completely covers the frame when closed), then is multiplied by a fullness factor — flat tab-tops use 1.5× while goblet pleats need 3× the finished width. Side hems (roughly 5 cm each edge) are added to each panel on top of that.
The cut length equals the desired finished drop — window height, plus the distance the rod sits above the window, minus any floor clearance — padded with a 10 cm header allowance (for the tape or fold at the top) and a 15 cm double bottom hem. Buying the full cut length ensures you have enough for levelling and hemming after hanging.
These are standard industry allowances; patterns with a vertical repeat require additional fabric equal to one full repeat per panel (not calculated here). Always add 5–10% extra for cutting waste and mismatched edges.
Frequently asked questions
Tab-top and flat panels work at 1.5× fullness. Eyelets and grommets look best at 2×. Pencil and pinch pleats need 2.5× for good gathering, and goblet or box pleats need 3× or more for a luxurious drape.
Measure from the floor (or window sill if you want café curtains) to where you want the top of the finished curtain to hang — usually 10–20 cm above the window frame. The calculator adds header and hem allowances automatically on top of that.
Yes. For fabrics with a vertical pattern repeat you need one full repeat of extra length per panel so you can match the pattern across panels. This calculator assumes plain or non-directional fabric; add one repeat per panel to the cut length if yours has a pattern.
Also known as
TG we-Calculate Editorial Team. (2026). Curtain Size Calculator — Fabric Width & Drop [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/curtain-size-calculator
TG we-Calculate Editorial Team. "Curtain Size Calculator — Fabric Width & Drop." TG we-Calculate. 2026. https://we-calculate.com/calculator/curtain-size-calculator.
TG we-Calculate Editorial Team, "Curtain Size Calculator — Fabric Width & Drop," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/curtain-size-calculator
@misc{wecalculate_curtain_size_calculator, title = {Curtain Size Calculator — Fabric Width & Drop}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/curtain-size-calculator}}, year = {2026}, note = {TG we-Calculate} }
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