Curtain Panel Calculator — How Many Curtain Panels Do I Need?
Enter your window width, panel width and desired fullness to find out exactly how many curtain panels to buy — plus total fabric area and the actual fullness you will achieve.
Unit
cm
cm
cm
Always rounded up so fabric covers the window with the desired fullness
- 1
Total fabric width needed
200 × 2 = 400Window width multiplied by the fullness factor. - 2
Panels needed (rounded up)
⌈ 400 ÷ 140 ⌉ = 3
How does this calculator work?
Panels needed = ⌈ window width × fullness / panel width ⌉. Standard fullness is 2× the window width; luxurious styles use 2.5–3×. Enter window width, standard panel width and drop to get the panel count, total fabric area and the actual fullness you will achieve after rounding up.
Formula
How this is calculated
The key concept is fullness: a flat curtain (1× fullness) would look sparse and let in light around the edges, so designers typically specify 1.5–3× the window width in fabric. A fullness factor of 2.0 — the most common recommendation — means you need curtain fabric totalling twice the window width. Since curtains come in fixed panel widths, you divide the total required width by the panel width and round up to the next whole panel.
For example, a 200 cm window at 2× fullness needs 400 cm of fabric. A standard 140 cm panel covers 140 cm, so you need ⌈400/140⌉ = 3 panels, giving you 420 cm of fabric and an actual fullness of 2.1×, which is slightly more than requested — this slight overage is normal and unavoidable when panels come in discrete widths.
The drop (length) affects only fabric area (not the panel count), which you need for ordering fabric by the metre or checking a fabric roll is long enough. The header allowance estimate (≈15% of panel width) covers the material gathered into pinch-pleats, pencil-pleats or eyelet headers — adjust to your specific tape or header style.
Frequently asked questions
1.5× is the minimum for a neat look and works well for lightweight sheers. 2.0× is the standard for most lined curtains and gives a generous gather. 2.5–3.0× is used for luxurious or theatrical drapes. Heavier fabrics (velvet, blackout) tend to use lower fullness (1.5–2×) because the fabric itself is thicker and provides body.
For a pair of curtains (one on each side of the window) you generally want an even number so the panels split symmetrically. If the calculator returns an odd number, round up to the next even number. For a single panel used as a room divider or to one side only, an odd count is fine.
Measure from the curtain rod or track to where you want the curtain to end, then add allowances: 15–20 cm at the top for the header/hooks, 10–15 cm at the bottom for the hem, and optionally 1–3 cm of 'puddle' if you want a pooled look. Enter the total including all allowances.
TG we-Calculate Editorial Team. (2026). Curtain Panel Calculator — How Many Curtain Panels Do I Need? [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/curtain-panel-calculator
TG we-Calculate Editorial Team. "Curtain Panel Calculator — How Many Curtain Panels Do I Need?." TG we-Calculate. 2026. https://we-calculate.com/calculator/curtain-panel-calculator.
TG we-Calculate Editorial Team, "Curtain Panel Calculator — How Many Curtain Panels Do I Need?," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/curtain-panel-calculator
@misc{wecalculate_curtain_panel_calculator, title = {Curtain Panel Calculator — How Many Curtain Panels Do I Need?}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/curtain-panel-calculator}}, year = {2026}, note = {TG we-Calculate} }
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