Curtain Panel Size & Quantity Calculator
Enter the window, rod, and retail-panel measurements to estimate how many panels to hang and packages to buy. The result also accounts for returns, center overlap, fullness, and the way you want the panels to meet the floor.
Panels to hang4
- Usable rod span (in)
- 84
- Total coverage width (in)
- 92
- Target total flat width (in)
- 184
- Packages to buy
- 4
- Extra panels in purchased packages
- 0
- Achieved fullness
- 2.26
- Target finished panel length (in)
- 95.5
- Shopping summary
- Buy 4 panels at least 52 in wide by 95.5 in long (4 packages). This gives 2.26× fullness.
Uses the listed flat panel width. Confirm whether a retailer lists one panel or a pair before ordering.
How to use this calculator
- Measure the outside width of the window frame, then enter the rod extension on each side.
- Add the return depth at each outer end and the overlap you want where the panels meet.
- Choose a fullness level, then enter the listed flat width of one panel and the number of panels in each package.
- Choose equal sides unless one panel will stack to one side, then enter the hanging-point-to-floor measurement and floor finish.
How curtain panel quantity is calculated
Start with the width the treatment must cover, rather than the glass alone. The usable rod span is the frame width plus the extension on both sides. The calculator then adds a return at each outside end and the center overlap. Those details need fabric even though they are not part of the visible opening.
The width calculation is S = W + 2E, then C = S + 2R + O, where W is frame width, E is extension per side, R is return per side, and O is center overlap. The target flat width is T = C × F, where F is the selected fullness.
Divide that target by the seller's flat width for one panel and round up: N0 = ceil(T ÷ P). If the panels will split evenly around the window, the result rounds up to an even quantity: N = 2 × ceil(N0 ÷ 2). Packages are also a whole-number purchase: Q = ceil(N ÷ K), where K is panels per package. The achieved fullness is A = (N × P) ÷ C, so it can be higher than the selected target after rounding.
Choosing the measurements that matter
Use the advertised ungathered, flat width of a single panel. A listing that says “52 in W” may mean one 52-inch panel, but some products are sold as a pair; the package field keeps that purchase detail separate from the number you hang. If the listing gives an already pleated or installed width, do not treat it as flat fabric width. Fixed pleat, wave, traverse, and made-to-measure systems often use their own ordering rules.
Fullness has the largest effect on panel count. A 2× setting means the flat fabric width is twice the coverage width before rounding. The extension, returns, and overlap matter most on smaller windows because they add a fixed amount of coverage. The tool reports the actual fullness from the panels you will hang, which is useful when a panel width forces a larger step than expected.
How finished length is estimated
The finished panel length begins with the distance from the panel's hanging point to the floor. A float subtracts 0.5 inch, a just-touch finish makes no adjustment, a break adds 1 inch, and a puddle adds 4 inches. Ready-made curtains come in fixed lengths, so choose the closest product length that can be hemmed or otherwise finished to the target.
What this estimate leaves out
This is a shopping estimate, not a hardware or workroom specification. It does not calculate stack-back, finial clearance, bracket placement, pattern matching, fabric yardage, hems, header construction, or shrinkage. Lining, fabric stiffness, and heading style can also change how a given fullness looks. Follow the hardware and curtain manufacturer's measuring instructions when they differ from this general method.
Worked example
For a 72-inch frame with a 6-inch extension and a 3-inch return on each side, plus a 2-inch center overlap, the usable rod span is 72 + 2 × 6 = 84 inches. Coverage is 84 + 2 × 3 + 2 = 92 inches. At 2× fullness, the target flat width is 184 inches.
With 52-inch-wide panels, ceil(184 ÷ 52) = 4 panels are required; four is already even. Sold one per package, that is four packages. The actual fullness is (4 × 52) ÷ 92 = 2.26×. If the hanging point is 96 inches above the floor and the panels float, the target finished length is 95.5 inches.
Common questions
How many curtain panels do I need for one window?
Divide the flat fabric width you need by the flat width of one panel, then round up. For curtains that meet in the middle, round that quantity up to an even number so both sides can use the same number of panels. The needed fabric width depends on the rod span, returns, overlap, and fullness.
Should curtain width be based on the window or the rod?
Base the calculation on the treatment coverage, which usually starts with the usable rod span instead of the window glass. Add fabric for the returns at both outer ends and for the center overlap. Measuring only the opening can leave the sides or center short.
What does 2× curtain fullness mean?
At 2× fullness, the panels’ total flat width is twice the width they cover after they are gathered on the rod. It is a common starting point for many rod-pocket and grommet panels, but fabric weight and heading style change the finished look. The calculator shows achieved fullness because whole panels may exceed the target.
Should I use the width of one panel or the pair?
Use the listed flat width of one individual panel in the panel-width field. Enter the number of panels included in one retail package separately. This distinguishes the quantity you need to hang from the number of packages you need to order.
Why did the calculator round my panel count to an even number?
An even count lets a center-opening treatment put the same number of panels on each side. Turn off equal panels for a one-way treatment, or when all panels will stack to one side. Package quantities can still create extra purchased panels even when the hanging count is odd.