Curtain Size Calculator
Calculate the panel width and length for curtains, including the fullness needed for a gathered look.
Formula and sources updated · Data sources · 1View algorithm, constants and default inputs (JSON)
About this calculator
Choose a fullness preset and hem finish to estimate equal-width panels. The rod preset extends 8 inches past each side; fabric area excludes hems, seams and pattern matching, so confirm finished measurements with the curtain maker.
Worked example
calculated with the default values below
Window width 60 in · Window height 60 in · Number of panels 2 · Fullness Standard gathered (2×) · Hem finish Floor length (1/2 in above floor) · Rod height above window 4 in Recommended rod width 76.0 in · Width per panel 76.0 in · Length per panel 63.5 in · Total fabric if panels were flat 67.0 sq ft
Method and assumptions
Fb = (W + 16) × f × (H + r + h) ÷ 144 Rod = window width + 16 in (8 in each side); panel width = rod × selected fullness ÷ panel count. Panel length = window height + rod rise + hem allowance. Flat fabric area excludes hems, seams and pattern matching. Choose a fullness preset and hem finish to estimate equal-width panels. The rod preset extends 8 inches past each side; fabric area excludes hems, seams and pattern matching, so confirm finished measurements with the curtain maker. Use the cited guidance and your own measurements, bills or product specifications to choose inputs. Sample defaults are not current local data.
Data sources
Use the cited guidance and your own measurements, bills or product specifications to choose inputs. Sample defaults are not current local data.
Disclaimer
These calculators provide planning estimates only. Building codes, wiring regulations and safety requirements differ by country and change over time, and nothing here replaces a licensed professional or a permit. For structural, electrical or gas work, follow local code and have the installation inspected.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
Fb = (W + 16) × f × (H + r + h) ÷ 144
- W
- Window width (in)
- f
- Fullness (1.5 / 2 / 2.5 / 1)
- H
- Window height (in)
- r
- Rod height (in)
- h
- Hang allowance (0 / 4 / −0.5 / 4)
Rod = window width + 16 in (8 in each side); panel width = rod × selected fullness ÷ panel count. Panel length = window height + rod rise + hem allowance. Flat fabric area excludes hems, seams and pattern matching.
Frequently asked questions
Why does the curtain rod width add sixteen inches to the window?
The tool sets recommended rod width to window width plus 16 inches so the panels clear the glass by about 8 inches each side when open. Fullness then scales panel width: sheer uses 1.5x, standard 2x, deluxe 2.5x, so a 60-inch window on standard needs a 76-inch rod and panels totalling 152 inches. The hem finish only shifts length, not width.
Which inputs and limits apply to Curtain Size Calculator?
Use the units shown beside each field. These are form limits, not recommended settings. Window width: 6–400 in; Window height: 6–300 in; Number of panels: 1–10; Rod height above window: 0–24 in Fb = (W + 16) × f × (H + r + h) ÷ 144 Rod = window width + 16 in (8 in each side); panel width = rod × selected fullness ÷ panel count. Panel length = window height + rod rise + hem allowance. Flat fabric area excludes hems, seams and pattern matching. Choose a fullness preset and hem finish to estimate equal-width panels. The rod preset extends 8 inches past each side; fabric area excludes hems, seams and pattern matching, so confirm finished measurements with the curtain maker. Use the cited guidance and your own measurements, bills or product specifications to choose inputs. Sample defaults are not current local data.
What is a complete worked example for Window width = 60 in; Window height = 60 in?
Inputs: Window width = 60 in; Window height = 60 in; Number of panels = 2; Fullness = Standard gathered (2×); Hem finish = Floor length (1/2 in above floor); Rod height above window = 4 in. Calculation: Fb = (W + 16) × f × (H + r + h) ÷ 144. Results: Recommended rod width = 76.0 in; Width per panel = 76.0 in; Length per panel = 63.5 in; Total fabric if panels were flat = 67.0 sq ft.