Roman blind fabric calculator
A Roman blind is a flat panel, so unlike a curtain it takes no fullness: the cloth across is the finished width plus a side turning at each edge, and a width is only joined when the blind is wider than the roll. Down the roll the cut is the finished drop plus an allowance to wrap the top batten and a hem deep enough to take the bottom bar, rounded up to whole pattern repeats on a patterned fabric. Lining is cut to the same length plus whatever the rod pockets consume.
Your blind and your fabric
Turnings, hems, rods and lining
1.9 m
1 cut of 182 cm. Rounded up to nearest 10 cm.
- Widths across per blind
- 1 width120 cm finished, plus 10 cm of turnings
- Cut length
- 182 cm160 cm drop, plus batten and hem
- Cuts in total
- 11 blind
- Lining to buy
- 2 m194 cm per cut, including 4 rod pockets
The lining length includes what those pockets consume. Where the rods actually sit is a workroom convention rather than arithmetic, and published methods differ on how the bottom section relates to the folds — so this tool does not assert one. As a guide, aim for a fold of 20–30 cm.
How we got this
- Widths across — 1 width120 cm finished + 10 cm of side turnings, on 140 cm cloth
- Cut length before matching — 182 cm160 cm drop + 10 cm over the batten + 12 cm hem
- Fabric required — 182 cm1 cut × 182 cm
- Lining required — 194 cm1 × (182 cm + 4 pockets × 3 cm)
How this calculator works
A Roman blind is a flat panel of cloth that pleats up on itself when it is raised. Flat is the word that matters: there is no fullness, so the arithmetic is much simpler than a curtain's and one thing dominates it entirely.
Across: the finished width plus a side turning at each edge, turned to the back. That is all. A width is only joined when the blind is wider than the usable roll, and each join costs two seam allowances — the same solver the curtain calculator uses, because the geometry is identical once fullness is taken out of it.
Down: the finished drop, plus an allowance to wrap the top batten and fasten behind it, plus a hem deep enough to take the bottom bar. The defaults are 10 cm and 12 cm, and both are editable.
Then the repeat. On a patterned fabric the cut length is rounded up to a whole number of pattern repeats, so the motif sits where you want it rather than wherever the roll happened to start. On a blind — a single flat panel where the pattern is on full display and there is no gather to disguise anything — this is not a refinement. It is usually the largest number in the calculation.
A worked example
A 120 cm by 160 cm blind in plain 140 cm fabric, lined, with 4 rod pockets. These are the calculator's own starting values, so the table below is the arithmetic the tool runs rather than a retelling of it.
| Step | Working | Result |
|---|---|---|
| Widths across | 120 cm finished + 10 cm of side turnings, on 140 cm cloth | 1 width |
| Cut length before matching | 160 cm drop + 10 cm over the batten + 12 cm hem | 182 cm |
| Fabric required | 1 cut × 182 cm | 182 cm |
| Lining required | 1 × (182 cm + 4 pockets × 3 cm) | 194 cm |
What the pattern repeat costs on a blind
Every row below is the same blind. Only the fabric changes.
| Pattern repeat | Cut length | Trimmed per cut | Fabric to buy |
|---|---|---|---|
| Plain | 182 cm | — | 1.9 m |
| 16 cm | 192 cm | 10 cm | 2.1 m |
| 32 cm | 192 cm | 10 cm | 2.3 m |
| 64 cm | 192 cm | 10 cm | 2.6 m |
The plain fabric needs 1.9 m. The large repeat needs 2.6 m for an identical finished blind — the difference is the matched cut plus the extra repeat allowed so you can choose where the motif falls. Neither figure is wrong; they are what the same blind costs in two different fabrics, and it is worth knowing before you fall in love with the second one. The pattern repeat calculator shows where the boundaries sit, and how little the drop sometimes has to change to cross one.
Rod pockets, and what this does not tell you
The lining carries the rod pockets, not the face fabric, so every pocket adds to the lining length and nothing to the fabric. The calculator allows 3 cm per pocket by default and lets you change both the count and the allowance.
It does not tell you where the rods go. That is deliberate. Fold depth and rod spacing follow a workroom convention rather than an arithmetic identity, and published methods disagree about how the bottom section should relate to the folds above it — some make it a full fold, some half, some size it so the stack is hidden when the blind is up. Every figure on this site is meant to be checkable against a source, and until one is recorded for rod spacing this tool asserts nothing about it.
What is safe to say as a guide: aim for a fold of 20 to 30 cm, which puts five or six pockets on a 160 cm blind and seven or eight on a tall one. Below about 15 cm the folds crowd; above about 35 cm they sag in the middle.
How to measure for this
- Decide inside or outside the recess. Inside gives a neat finish and needs the width taken at three heights, using the narrowest. Outside covers a poor frame and overlaps the opening by 5 to 10 cm each side.
- Measure the finished width. The width of the made-up blind, which is the width of the batten it hangs from — not the width of the glass.
- Measure the finished drop. From the top of the batten down to where the bottom of the blind should sit. Inside a recess, stop just short of the sill.
- Take the roll width and the repeat. Both from the fabric label. Enter 0 for the repeat if the fabric is plain.
- Count the rod pockets. Aim for a fold of 20 to 30 cm. The lining allowance follows from the count; where the rods sit is a workroom decision.
Inside a recess, measure the width at the top, middle and bottom and use the narrowest — very few window openings are square, and a blind cut to the widest measurement will jam. Take about a centimetre off that narrowest figure so the blind clears the sides as it travels.
What this assumes
- A flat blind, not a cascade or a relaxed blind. Those hold a permanent fold at the bottom and need extra length for it. Add that length to the drop before entering it.
- A straight pattern repeat. On a half-drop each additional width needs an extra half repeat to line up. This will under-order on one, and warns when a repeat is entered.
- Side turnings on the two outer edges only. A joined blind is charged two seam allowances at each join instead, not a turning per width — the same rule as a curtain.
- The roll width as entered. A heavy selvedge that has to be cut away is not deducted. Measure the usable cloth and enter that.
- Rounding is always up, at every step. Buying too much costs a few pounds; buying too little means matching a dye lot that may have sold out.
For curtains at the same window, the curtain fabric calculator handles fullness and headings, and the curtain lining calculator works out lining on its own narrower roll. If your blind is wider than the roll, the fabric width chart shows which widths a wider cloth would avoid joining.
Common questions
- How much fabric do I need for a Roman blind?
- The finished drop plus about 22 cm of allowances — roughly 10 cm to wrap the batten and 12 cm for a hem deep enough to take the bottom bar — by the finished width plus a turning each side. On a plain fabric that is the whole answer for a blind narrower than the roll. On a patterned fabric the cut is then rounded up to a whole number of repeats, which can add a great deal.
- Does a Roman blind need extra fabric for fullness?
- No. That is the main difference from a curtain. A Roman blind hangs flat against the window and pleats only when it is drawn up, so the cloth across is the finished width and nothing more. A curtain at 2× fullness needs twice its track width; a blind of the same width needs one width of cloth.
- Where should the seam go if the blind is wider than the fabric?
- A seam down a Roman blind is visible whenever the blind is down, which is most of the time. Standard workroom practice is a full width in the centre with equal part-widths joined either side, so the two seams sit symmetrically. A single seam falling near the middle of the blind is the arrangement to avoid.
- How many folds should a Roman blind have?
- As a guide, aim for a fold of 20 to 30 cm — so a 160 cm blind usually takes five or six. This calculator allows for the lining each rod pocket consumes but does not tell you where the rods go: published workroom methods differ on how the bottom section relates to the folds, and the figures on this site are meant to be checkable against a source.
- Do I need lining for a Roman blind?
- Almost always. The lining carries the rod pockets and the rings, protects the face fabric from sunlight, and gives the blind enough body to fold cleanly. Set the lining width to 0 in the calculator for an unlined blind, which is worth considering only on a heavy fabric where the folds will hold anyway.
Related tools
Curtain fabric calculator
Track width, drop, fullness and pattern repeat in; metres or yards to buy out, with every allowance adjustable.
Pattern repeat calculator
The cut length a repeat forces, what is trimmed from every piece, and what matching the design costs.
Curtain lining calculator
Lining on its own narrower roll, from the flat width your curtains already need.
Fabric width chart
Standard roll widths in both systems, and the gap between the label and the cloth.
Fabric yardage calculator
Piece size, how many, roll width — the length to buy, and the strip you pay for but never cut.