Home & Craft curtain planner
Plan fullness before you buy or cut
Turn a pole or track width into the flat curtain width you need, then plan ready-made panels or whole fabric widths. Optional cut-length planning keeps vertical pattern-repeat rounding visible instead of hiding it.
Minimum ready-made panels
—Calculation breakdown
This tool plans width and fullness from the measurements you enter. Heading-specific workroom rules, horizontal pattern matching, shrinkage and other fabrication allowances are not added unless you include them in your own inputs.
How the Curtain Fullness Calculator Works
Curtain fullness connects the width a closed curtain must cover with the amount of flat curtain material available before gathering, pleating, or heading construction shapes the finished curtain.
The Curtain Fullness Calculator keeps those measurements separate. It can:
- calculate the target flat curtain width;
- determine the minimum number of ready-made panels;
- calculate the whole fabric widths needed for sewn curtains;
- show the fullness actually achieved after material rounding;
- test a specific number of panels you already own or plan to buy;
- estimate cut length for each fabric width;
- adjust cut length for a vertical pattern repeat;
- calculate total fabric length.
What Curtain Fullness Measures
Curtain fullness compares two widths:
Coverage width — the horizontal distance the closed curtains need to cover.
Flat curtain width — the combined width of the curtain material before gathering or pleating.
The basic relationship is:
Fullness = Flat curtain width ÷ Coverage width
For example, 144 inches of flat curtain width across a 72-inch track gives:
144 ÷ 72 = 2× fullness
When planning curtains, reverse the formula:
Target flat width = Coverage width × Target fullness
For a 72-inch coverage width at 2× fullness:
72 × 2 = 144 in
The exact target is therefore:
144 inches of flat curtain width
Actual panels or whole fabric widths may provide more than this exact amount, so the calculator also reports the fullness ultimately achieved.
Start With the Width the Curtains Need to Cover
Enter the full pole or track width the closed curtains need to cover.
If returns, center overlap, or another horizontal allowance is required and is not already included in that measurement, enter the combined extra coverage for the complete curtain setup.
Suppose the measurement excludes:
- 3-inch return on the left;
- 3-inch return on the right;
- 4-inch center overlap.
Combined additional coverage:
3 + 3 + 4 = 10 in
The calculator uses:
Effective coverage = Pole or track width + Total extra coverage
Then:
Target flat width = Effective coverage × Fullness ratio
For example:
- Track width: 72 in
- Additional coverage: 4 in
- Target fullness: 2×
Effective coverage:
72 + 4 = 76 in
Target flat width:
76 × 2 = 152 in
Do not add the same allowance twice.
If the entered pole or track measurement already includes the complete horizontal coverage you intend to use, leave the extra-coverage input at zero.
Target Fullness vs Achieved Fullness
The target fullness is the ratio selected for planning.
The achieved fullness is the ratio produced by the actual panels or fabric widths used.
They may differ because curtains and fabric are normally available in fixed widths.
The calculator uses:
Achieved fullness = Actual total flat width ÷ Effective coverage
Suppose the exact target is:
168 in
but the required whole panels provide:
200 in
The achieved fullness must be calculated from the actual 200 inches.
It should not simply be reported as the original selected target.
This distinction is useful when comparing different panel widths, fabric widths, or purchase quantities.
Calculate How Many Ready-Made Curtain Panels You Need
Ready-made curtains are purchased as complete panels, so a fractional panel requirement must be rounded upward.
First:
Raw panel requirement = Target flat width ÷ Flat width of one panel
Suppose:
- Coverage width: 84 in
- Target fullness: 2×
- Flat width of one panel: 50 in
Target flat width:
84 × 2 = 168 in
Raw panel requirement:
168 ÷ 50 = 3.36 panels
A quantity of 3.36 panels cannot be purchased or used as complete ready-made panels.
Round upward:
Minimum panels = 4
Actual flat width:
4 × 50 = 200 in
Achieved fullness:
200 ÷ 84 ≈ 2.38×
The result therefore becomes:
| Result | Value |
|---|---|
| Target fullness | 2× |
| Target flat width | 168 in |
| Minimum whole panels | 4 |
| Actual flat width | 200 in |
| Achieved fullness | 2.38× |
The achieved fullness is higher than the target because complete panels provide more width than the exact mathematical requirement.
Sailrite’s window-treatment measuring guidance likewise describes adding curtain fullness by multiplying the total width by a chosen fullness factor.
Equal Curtain Pairs Require an Even Number of Ready-Made Panels
When equal-pair mode is selected, each side must contain the same number of complete ready-made panels.
Suppose the minimum calculated quantity is:
3 panels
That could produce:
- 1 panel on one side;
- 2 panels on the other.
It would not create an equal curtain pair.
The calculator therefore moves to the next even quantity:
3 minimum panels → 4 panels for an equal pair
The result can then show:
- Total panels: 4
- Panels per curtain: 2
This even-number rule applies to complete ready-made panels.
Sewn fabric widths can use different construction logic.
Check a Specific Number of Curtain Panels
Sometimes the goal is not to find the minimum quantity.
You may already own curtains or be considering a specific pack size and want to know whether that quantity provides enough fullness.
Suppose a single-curtain or one-way-draw setup uses:
- Coverage: 84 in
- Target fullness: 2×
- Panel width: 50 in
- Planned panels: 3
Actual flat width:
3 × 50 = 150 in
Achieved fullness:
150 ÷ 84 ≈ 1.79×
The target flat width is:
84 × 2 = 168 in
Width shortfall:
168 − 150 = 18 in
The three-panel setup therefore provides:
1.79× achieved fullness
and remains:
18 inches short of the 2× target
If four panels are used:
4 × 50 = 200 in
Achieved fullness:
200 ÷ 84 ≈ 2.38×
This mode lets you compare material you already own or a specific proposed purchase against the target instead of calculating only the minimum recommended quantity.
Plan Whole Fabric Widths for Sewn Curtains
For curtains made from fabric, enter the usable width of one fabric drop.
Usable width is the amount that can actually contribute to curtain fullness after any width intentionally excluded from the calculation.
For example, if selvage removal or another construction requirement reduces a nominal 56-inch fabric to:
54 inches usable
enter:
54 in
The calculator uses:
Raw fabric-width requirement = Target flat width ÷ Usable fabric width
Suppose:
- Coverage: 72 in
- Target fullness: 2×
- Usable fabric width: 54 in
Target flat width:
72 × 2 = 144 in
Raw requirement:
144 ÷ 54 ≈ 2.67 widths
Round upward:
3 whole fabric widths
Actual flat width:
3 × 54 = 162 in
Achieved fullness:
162 ÷ 72 = 2.25×
The calculator therefore reports:
| Result | Value |
|---|---|
| Target flat width | 144 in |
| Raw fabric-width requirement | 2.67 |
| Whole fabric widths required | 3 |
| Actual usable flat width | 162 in |
| Achieved fullness | 2.25× |
The minimum-width result is the smallest whole number of fabric widths that reaches or exceeds the selected fullness target.
A curtain maker can intentionally choose fewer widths and accept lower fullness, but that construction would no longer meet the target entered into the calculator.
Ready-Made Panels and Fabric Widths Use Different Pair Rules
Ready-made panels and uncut fabric widths should not be treated as interchangeable materials.
| Material | What Remains Whole | Equal-Pair Handling |
|---|---|---|
| Ready-made panels | Each completed curtain panel | Equal pairs require an even number of panels |
| Fabric widths | Each full-width fabric drop before sewing | An odd total may sometimes be divided between two curtains during construction |
Suppose a sewn curtain pair requires:
3 fabric widths
Three finished ready-made panels cannot create two equal curtains without physically altering one panel.
Three fabric widths, however, may sometimes be constructed as:
1.5 widths per curtain
One full fabric width can be split lengthwise, with one half incorporated into each curtain.
The total remains:
3 widths
rather than automatically increasing to four.
Whether this construction is appropriate depends on factors such as:
- fabric design;
- motif position;
- seam placement;
- fabric stability;
- heading style;
- workroom method.
The calculator exposes the fractional width-per-curtain result rather than hiding that construction assumption.
Why a Small Change in Usable Fabric Width Can Add a Whole Width
Fabric-width planning changes in steps.
A small reduction in usable width can therefore cross a threshold and require an additional complete fabric drop.
Suppose the target flat width is:
144 in
With 48 inches usable per width:
144 ÷ 48 = 3 widths
Exactly three widths are sufficient.
Now suppose each width provides only:
47 in usable
Then:
144 ÷ 47 ≈ 3.06 widths
Three widths provide:
3 × 47 = 141 in
Shortfall:
144 − 141 = 3 in
To reach the target, the result must increase to:
4 whole widths
This is why the calculator asks for usable fabric width rather than assuming the entire nominal fabric width contributes to curtain fullness.
Curtain Fullness Controls Width, Not Curtain Drop
Fullness determines the amount of fabric required horizontally.
Curtain drop determines the vertical length.
These calculations remain separate.
Changing a curtain from an 84-inch finished drop to a 96-inch finished drop does not by itself change the number of fabric widths required to achieve the selected fullness.
It changes the length required for each fabric drop.
Calculate the Base Cut Length
When fabric-length planning is enabled:
Base cut length = Finished curtain drop + Top and bottom allowance
Suppose:
- Finished curtain drop: 90 in
- Combined top and bottom allowance: 10 in
Base cut length:
90 + 10 = 100 in
Each full fabric width therefore needs a base cut length of:
100 inches
before any vertical pattern-repeat adjustment.
Adjust Cut Length for a Vertical Pattern Repeat
A fabric with a vertical pattern repeat may require each cut to end on a complete repeat interval.
Suppose:
- Base cut length: 100 in
- Vertical repeat: 18 in
Complete repeat multiples include:
18, 36, 54, 72, 90, 108, 126…
The first complete multiple that reaches or exceeds 100 inches is:
108 in
Pattern-adjusted cut length:
108 in
The extra length created by repeat alignment is:
108 − 100 = 8 in per width
If the base cut length already falls exactly on a complete repeat, the calculator keeps that value rather than automatically adding another full repeat.
For example:
- Base cut: 108 in
- Repeat: 18 in
Since:
108 ÷ 18 = 6
the cut is already aligned with a complete repeat.
Adjusted cut length remains:
108 in
Calculate Total Fabric Length
Once the cut length for one fabric width is known:
Total fabric length = Cut length per width × Number of whole fabric widths
Suppose:
- Fabric widths required: 3
- Pattern-adjusted cut length: 108 in
Total fabric:
108 × 3 = 324 in
Convert inches to yards:
324 ÷ 36 = 9 yd
Total fabric requirement:
9 yards
For centimeter-based planning, the corresponding total can be displayed in metres.
This keeps three different stages visible:
Widths required for fullness → Cut length for each width → Total fabric length
Pattern Repeat Can Add Material Without Changing Fullness
A vertical pattern repeat affects fabric length, not the flat width used to create curtain fullness.
Suppose three widths are already required.
Changing the cut length from:
100 in
to:
108 in
because of a pattern repeat does not change:
- the number of widths;
- the total flat curtain width;
- the achieved fullness.
It changes only the total linear fabric requirement:
Without pattern adjustment:
100 × 3 = 300 in
With pattern adjustment:
108 × 3 = 324 in
Additional fabric:
324 − 300 = 24 in
The distinction prevents vertical pattern matching from being mixed into the horizontal fullness calculation.
Use Consistent Measurements
For reliable results:
- measure the pole or track width that the curtains actually need to cover;
- include extra coverage only when it is not already part of that width;
- use the flat panel width rather than the gathered width of a ready-made curtain;
- enter usable fabric width when part of the nominal width will not contribute to fullness;
- use the same measurement unit for related width inputs;
- enter the finished curtain drop separately from fullness;
- include only the top and bottom allowances relevant to the planned construction;
- use the actual vertical repeat of the selected fabric when pattern matching is required.
Recalculate if:
- the track or pole width changes;
- the fullness target changes;
- panel width changes;
- fabric usable width changes;
- the curtain drop changes;
- construction allowances change;
- another fabric with a different repeat is selected.
Construction Allowances the Calculator Does Not Add Automatically
The calculator deliberately avoids inserting a generic waste factor.
Its fabric-length mode can account for:
- finished curtain drop;
- entered top and bottom allowance;
- straight vertical pattern repeat.
It does not automatically add:
- fabric shrinkage;
- general shopping waste;
- cutting waste;
- side hems not already reflected in usable width;
- selvage deductions not already reflected in usable width;
- half-drop pattern matching;
- horizontal motif matching;
- extra repeat length used specifically to position a motif;
- workroom-specific seam allowances;
- heading-specific construction allowances not entered by the user.
These requirements can vary substantially by curtain style, fabric, and sewing method.
Keeping them outside the core calculation prevents an unexplained allowance from being hidden inside the result.
Calculation Method
The Curtain Fullness Calculator separates width planning from vertical fabric-length planning.
For fullness calculations, it:
- determines effective coverage width;
- multiplies coverage by the selected fullness ratio;
- calculates the exact target flat width;
- converts that target into whole ready-made panels or whole fabric widths;
- applies equal-pair rounding to complete ready-made panels when selected;
- calculates actual flat width after material rounding;
- reports the achieved fullness;
- compares a specific planned panel quantity with the selected target when requested.
For fabric-length planning, it:
- adds the entered top and bottom allowance to the finished curtain drop;
- adjusts the cut length upward to a complete vertical pattern repeat when required;
- multiplies the final cut length by the number of whole fabric widths;
- converts the resulting linear fabric requirement into yards or metres where appropriate.
The result is a transparent material-planning calculation.
It does not replace the final construction plan for a particular heading style, seam layout, pattern match, or curtain workroom method.