Updated 19 September 2026 · Planning guidance with linked calculators
Curtain Fabric Calculator checkpoint
A 2.45 m installed track needs full-length curtains finishing at 2.35 m. The usable fabric width is 1.37 m. A provisional 320 mm extra allowance per drop is entered; it is not an automatic pattern-repeat calculation.
Inputs used
| Track or rod width | 2.45 m |
|---|---|
| Finished curtain length | 2.35 m |
| Fabric width | 1.37 m |
| Fullness multiplier | 2.2 |
| Hem allowance per drop | 0.4 m |
| Pattern repeat allowance | 0.32 m |
Calculator result
- Fabric widths
- 4 widths
- Cut drop
- 3.07 m
- Fabric required
- 12.28 m
Decision from this checkpoint
Treat the fabric quantity as a planning order and have the heading style and repeat-matching method checked before expensive fabric is cut.
- Measure the installed track, not the glass width.
- Confirm whether the workroom needs extra matching or shrinkage allowance.
Tools referenced in this project
- Curtain Fabric Calculator
- Curtain Fullness Calculator
- Curtain Rod Length Calculator
- Blind Size Calculator
Measure the treatment position, not only the glass
Decide whether the rod or track will sit inside the reveal, on the frame, or extend beyond it. Measure the intended finished hardware width and the drop from that hardware position to the chosen end point. Repeat the measurement at several points on an older opening. The curtain calculation should begin from these finished dimensions because moving the rod later changes both width and drop.
Fullness changes fabric width
Finished curtain width is normally wider than the track or rod span because the fabric is gathered or pleated. The fullness factor is a design and heading choice, not a constant. Multiply the covered width by the chosen fullness, then divide the result across the number of panels. Check whether the selected heading tape, rings, eyelets, or pleat style has its own recommended fullness before finalising the fabric quantity.
Convert finished drop into cut length
The finished drop does not include every allowance needed for cutting. Add the heading allowance, bottom hem, any turnings, and pattern positioning required by the chosen construction method. For a repeat of 0.32 m and a finished length plus hems of 2.75 m, rounding to the next full repeat gives 2.88 m before any extra workroom requirements. The checkpoint instead adds a provisional 0.32 m allowance to produce 3.07 m; it does not perform repeat alignment. Confirm the actual cut length with the workroom. This is why two fabrics with the same width can require different total metres.
Count widths and allow for matching
Compare the required flat fabric width with the usable fabric width to find how many widths are needed across the treatment. Multiply that count by the adjusted cut length. For patterned fabric, consider whether joins must match across widths. Offcuts can sometimes be reused for tiebacks or small accessories, but do not assume they reduce the main order until the cutting plan confirms it.
Check hardware and installation separately
Curtain fabric calculations do not establish the capacity of rods, brackets, tracks, anchors, or the wall. Confirm span, bracket spacing, fabric weight, and fixing requirements using the hardware instructions and suitable installation guidance. Keep those checks alongside the fabric order so the treatment can be installed as planned.