To calculate how much curtain fabric you need, work out the number of fabric widths required and multiply that number by the cut drop. The essential measurements are the pole or track width, finished curtain drop, fabric width, fullness, making allowance and vertical pattern repeat.
For patterned fabric, the cut drop usually needs to be rounded up to a complete pattern repeat so adjacent widths can be matched. This is why two fabrics used for the same window can require different metreage.
Reviewed and updated by The Millshop Online fabric team: August 2026.
Curtain fabric calculation at a glance
| Input | What it means | Where to find it |
|---|---|---|
| Pole or track width | The usable width to be covered, excluding decorative finials | Measure the installed pole or track |
| Finished drop | The finished length from the chosen measuring point to the curtain hem | Measure at the window |
| Fullness | The extra width used to create pleats or folds | Heading instructions or curtain maker |
| Fabric width | The usable width of one fabric width | Product specification |
| Pattern repeat | The vertical distance before the design repeats | Product specification |
| Making allowance | Extra length for the heading, hems and finishing | Making method or curtain maker |
Check all measurements before ordering curtain fabric by the metre. The worked example below is a guide; heading methods and professional workrooms can use different allowances.
Step 1: measure the pole or track width
Measure the usable pole or track rather than the glass or window frame. Exclude finials from a pole measurement. For an overlapping track, include the overlap according to the track instructions.
Use the same unit throughout the calculation. This guide works in centimetres and converts the final figure into metres.
Step 2: choose the curtain fullness
Fullness is the relationship between the flat fabric width and the finished curtain width. Double fullness means using approximately twice the pole or track width before the heading is formed.
| Heading | Indicative fullness | Important note |
|---|---|---|
| Pencil pleat | Often around 2 to 2.5 times | Check the tape instructions |
| Eyelet | Often around 2 times | Ring size and spacing affect the result |
| Double or triple pinch pleat | Often around 2 to 2.5 times | Confirm with the maker before cutting |
| Wave | Determined by the track system | Use the system supplier's specification |
Our curtain heading styles guide explains how each heading changes the appearance and amount of fabric required.
Step 3: calculate the number of fabric widths
First calculate the total flat width required:
Pole or track width × fullness = total flat fabric width
Then divide by the usable fabric width and always round up to the next whole width:
Total flat fabric width ÷ usable fabric width = number of fabric widths
If the answer is 3.2, you need four full widths, not 3.2 widths. For a pair of curtains, plan how the widths will be distributed between the left and right curtain before cutting.
Step 4: calculate the raw cut drop
The cut drop is the length of each width before the curtain is made. For plain fabric, start with:
Finished curtain drop + heading and hem allowances = raw cut drop
The correct allowance depends on the heading and construction method. Do not automatically use an allowance from another project. A professional maker may also require extra fabric for trimming, squaring or weighting.
Step 5: allow for the pattern repeat
For a patterned fabric, round the raw cut drop up to the next complete vertical pattern repeat. A useful formula is:
Matched cut drop = round up (raw cut drop ÷ vertical repeat) × vertical repeat
For example, if the raw cut drop is 250 cm and the vertical repeat is 64 cm, 250 ÷ 64 = 3.91. Round this up to four repeats: 4 × 64 cm gives a matched cut drop of 256 cm.
Some fabrics have a half-drop, offset or directional design. Check the full product specification and plan the layout before cutting. Large florals, leaves, birds, stripes and art deco designs can all require careful placement. See our curtain fabric pattern guide when comparing designs.
Step 6: calculate the total metres
Multiply the number of widths by the matched cut drop:
Number of widths × matched cut drop = total fabric length
Convert centimetres to metres by dividing by 100, then round up to the ordering increment available for that fabric. Add any extra amount required for tiebacks, cushions, testing or a workroom allowance.
Worked curtain fabric calculation
Assume the following measurements:
- Pole width: 240 cm
- Fullness: 2 times
- Usable fabric width: 137 cm
- Finished drop: 220 cm
- Making allowance for this example: 30 cm
- Vertical pattern repeat: 64 cm
- Total flat width: 240 × 2 = 480 cm.
- Number of widths: 480 ÷ 137 = 3.51, rounded up to four widths.
- Raw cut drop: 220 + 30 = 250 cm.
- Matched cut drop: 250 ÷ 64 = 3.91, rounded to four repeats. 4 × 64 = 256 cm.
- Total fabric: 4 × 256 cm = 1,024 cm, or 10.24 metres.
The calculated minimum in this example is 10.24 metres. The order should then be rounded up to the fabric's permitted increment and adjusted for any additional making allowance. Without pattern matching, the same window would use four raw drops of 250 cm, or 10 metres, showing how the repeat changes the order.
Should curtain lining be calculated separately?
Yes. Face fabric, lining and interlining are normally calculated separately because their widths, construction and allowances may differ. A plain lining will not usually need the same pattern-matching allowance as the face fabric.
Plan the layers together so the finished curtains are compatible with the heading and hardware. Read our curtain lining and interlining guide before choosing standard, blackout, thermal or interlining fabric.
Common curtain fabric calculation mistakes
- Measuring the window instead of the installed pole or track.
- Including the decorative finials in the pole width.
- Forgetting fullness.
- Using the nominal fabric width instead of the usable width.
- Ignoring the vertical pattern repeat or half-drop layout.
- Rounding the number of widths down.
- Using one standard making allowance for every heading.
- Forgetting that lining and interlining require separate calculations.
Bay windows need additional care because each section and return can affect the finished arrangement. Use our bay-window measuring guide or ask a curtain maker to confirm the measurements.
Curtain fabric ordering checklist
- Measure the installed pole or track at least twice.
- Confirm the finished drop and heading style.
- Check the usable fabric width and vertical pattern repeat.
- Round the number of fabric widths up.
- Round patterned cut drops up to complete repeats.
- Calculate lining and interlining separately.
- Order a sample to check colour, scale and handle.
- Have a professional maker confirm the quantity if the project is complex.
Frequently asked questions
How much extra curtain fabric is needed for pattern matching?
It depends on the vertical repeat and the number of widths. Each raw cut drop is normally rounded up to a complete repeat, so a larger repeat can add a significant amount across a wide window.
Do I multiply curtain width by two?
Many headings use approximately double fullness, but not every system does. Use the chosen heading or track instructions rather than assuming a fixed multiplier.
Is the cut drop the same as the finished drop?
No. The cut drop includes additional fabric for headings and hems, and it may also be rounded up for pattern matching.
Should I round the final fabric quantity up?
Yes. Round up to the ordering increment and include any allowance requested by the person making the curtains. It is much easier to use a small surplus than to correct an order that is short.
This calculation provides a dependable estimate when all the inputs are known. For unusual windows, expensive fabrics, large repeats or made-to-measure curtains, confirm the figures with the maker before placing the final order.
