1. Determine rod width
If the rod is installed, the measured rod width is used directly. Before installation, rod width equals window width plus the left and right extensions.
Curtain Size Calculator
Plan curtain rod width, target fullness, panel width, finished length, and ready-made panel quantities from your actual measurements.
Use Custom Size when planning curtain dimensions, or Ready-Made Panels when choosing store-bought panels. Enter the measurements and product sizes you actually plan to use.
Region & Unit
US mode uses inches. Canada mode uses centimetres. Existing measurements are converted when you switch regions.
Measurement Setup
Choose whether the rod is already installed so the calculator can use the correct measurements.
Rod Extension
Add the planned rod projection beyond the window on each side.
Result Mode
Choose whether you need custom curtain dimensions or a ready-made panel purchase plan.
Heading & Fullness
Heading style provides planning guidance only. Your selected fullness remains the value used by the calculator.
Not sure which heading to use? Choose the fullness you want directly.
Fullness
Drop Style
These are planning presets. Use Custom when you want a different adjustment.
Custom Panel Plan
Choose how many curtain panels you plan to make or order.
Number of Panels
Results update automatically when the required inputs are complete.
Your curtain sizing plan
Enter your curtain measurements to get a sizing plan. No sample measurements are inserted into the calculator.
Estimate disclaimer: This curtain sizing result is for planning purposes only. Confirm the product's measurement instructions, actual panel width and length, heading construction, hardware position, and installation details before ordering or altering curtains.
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How the Curtain Size Calculator Works
The calculator separates rod geometry, fullness, finished length, and panel purchasing into distinct steps. It uses the same production calculation for both the interactive result and the worked examples below.
2. Apply curtain fullness
Total flat curtain width equals rod width multiplied by the selected fullness factor. Heading style only supplies a planning range; it does not replace your selected value.
3. Resolve panel width or purchase count
Custom Size divides the required total width by your planned panel count. Ready-Made Panels compares the required width with one product panel's width and applies the selected Single, Pair, or Flexible arrangement rule.
4. Match finished length
Finished length starts with the relevant hanging measurement and adds the selected drop adjustment. Ready-made mode then chooses the smallest entered available length that is long enough for that finished length.
Formula
Rod width
Window width + left extension + right extension
Required total curtain width
Rod width × fullness factor
Custom panel width
Required total curtain width ÷ planned panel count
Achieved fullness
Purchased panel count × stock panel width ÷ rod width
Finished curtain length
Base hanging measurement + drop adjustment
Ready-made stock length
Smallest entered available length that is at least the finished length
Hemming amount
Hemming amount = recommended stock length − finished curtain length. This shows how much extra ready-made curtain length is available to remove when a longer stock size is selected.
Typical Fullness by Heading Style
- Grommet / Eyelet: 1.5×–2.0×
- Rod Pocket: 1.5×–2.0×
- Tab Top / Ring Top: 1.5×–2.0×
- Pencil Pleat: 2.0×–2.5×
- Pinch Pleat: 2.0×–2.5×
- Sheer Curtain: 2.0×–3.0×
These ranges are planning guidance only. The calculator always uses the fullness value you select.
When to Use This Calculator
- • Plan rod width before installing curtain hardware.
- • Choose total curtain width for a target fullness.
- • Split custom curtain width across one or more panels.
- • Compare single-panel and paired ready-made arrangements.
- • Check whether listed ready-made lengths are long enough.
- • Estimate how much a longer ready-made panel may need hemming.
Worked Examples Using the Production Calculation
These examples call the same calculateCurtainSize() production function as the interactive calculator rather than using hand-written result values.
Custom Size: two panels
A 60 in window uses 6 in rod extensions on both sides. The planned rod is 4 in above the window, the window-top-to-finish measurement is 80 in, and the target fullness is 2.0×.
- Rod width
- 72 in
- Total curtain width
- 144 in
- Width per panel
- 72 in
- Finished length
- 84 in
Ready-Made: symmetrical pair
Using the same window and fullness, suppose the selected product is 50 in wide per panel and is available in 63, 84, 95, and 108 in lengths.
- Panels to buy
- 4
- Recommended length
- 84 in
- Achieved fullness
- 2.78×
- Hemming amount
- 0 in
Assumptions and Limitations
This version is designed for ordinary straight curtain rods and curtain panels. Heading style supplies fullness guidance only, and the Hover, Kiss Floor, Slight Break, and Puddle values are planning presets rather than universal manufacturer rules.
It does not estimate fabric yardage, pattern repeat, lining, seam or hem allowance, sewing waste, ring count, curtain cost, motorized systems, bay windows, corner windows, or curved tracks. Ready-made length matching uses only the product lengths you enter.
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Curtain Size Calculator FAQ
How wide should curtains be compared with the rod?
Curtain width is commonly planned as a multiple of rod width rather than as a one-to-one match. This calculator multiplies the rod width by the fullness factor you choose, from 1.0× to 3.0×. A higher factor creates more fabric width across the same rod.
What does curtain fullness mean?
Fullness is the ratio between the total flat curtain width and the rod width. For example, 2.0× fullness means the flat curtain width is twice the rod width. Heading style can influence common planning ranges, but the calculator always uses the fullness value you select.
Should I use one curtain panel or a pair?
Use Single Panel only when one ready-made panel can provide the full target width by itself. Symmetrical Pair rounds the required quantity up to the smallest even number. Flexible Arrangement uses the minimum whole-panel quantity without an odd-or-even restriction.
Why can the calculator recommend more ready-made panels than expected?
Ready-made panels are purchased as whole pieces. If the required flat curtain width falls between whole-panel quantities, the calculator must round up. Pair mode may round up again to keep the final quantity even.
How is curtain length calculated?
The calculator starts with the measured distance from the hanging point to the desired finish. If the rod is not installed, it adds the planned rod height above the window to the window-top-to-finish measurement. The selected drop adjustment is then added to that base length.
What if none of the available panel lengths is long enough?
The result is marked Custom Length Recommended. The calculator does not invent a standard product size. Check another ready-made size, a different product, or a custom curtain option.
Does heading style automatically change the fullness calculation?
No. Heading style only provides a typical fullness range for planning. It does not lock the formula or silently replace a fullness value you have already chosen.
Does this calculator estimate fabric yardage or sewing allowances?
No. This version plans rod width, fullness, finished curtain dimensions, ready-made panel quantity, available length matching, and possible hemming. Fabric yardage, pattern repeat, lining, seams, hems, sewing waste, and ring counts are outside its scope.
Measurement Review Before You Order
Confirm the curtain manufacturer's measurement instructions, the actual panel width and available lengths, the heading design, the hardware position, and the intended finished position before purchasing or altering curtains. This calculator is a planning tool, not a product-specific installation specification.