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Roman Blind Calculator

Plan standard and cascade roman blinds from a recess or exact measurement. This free Roman blind calculator runs in your browser, stays free to print, and does not take payment or collect form data.

Estimation disclaimer. Figures are a transparent planning estimate for fabric and component quantities. They are not a trade cutting ticket and are not presented as workroom-accurate. Confirm allowances with your fabric, lining, headrail system and maker before cutting.

UnitsMillimetresCentimetresInches

Blind style

StandardHangs flat when lowered. Extra fabric is hems and top allowance only.CascadeKeeps soft folds when down. Extra drop is fold count × cascade depth.

Mount

Recess fitDeducts the width and drop clearances from the opening.Exact fitUses your figures as the finished size, for outside or already-cleared measurements.

WidthExample 1100 mm is loaded so the diagram can be inspected. Replace it with your window.DropMeasure the fabric drop you want to cover, not including a separate headrail unless you intend that.

Pull sideRightLeft

Planning allowances (editable, millimetres)

Leave a box blank to use the documented default. Allowances stay in millimetres even when the window is entered in centimetres or inches.

Recess width clearanceDeducted from opening width for a recess fit. Default 10 mm.Recess drop clearanceDeducted from opening drop for a recess fit. Default 5 mm.Side turning each sideAdded twice to finished width for the face cut. Default 50 mm.Bottom hemAdded to the face cut drop. Default 80 mm.Top allowanceAdded to the face cut drop for the headrail attachment. Default 50 mm.Target fold sizeUsed to choose fold count. Default 250 mm.Cascade depth per foldExtra drop per fold for cascade style. Default 50 mm.Lining width extraAdded to finished width for the lining cut. Default 40 mm.Lining drop extraAdded to finished drop for the lining cut. Default 40 mm.Rod insetTaken off finished width so rods sit inside the turnings. Default 20 mm.Column edge insetDistance from each side to the first and last cord column. Default 80 mm.Maximum column spacingPlanner adds columns until spacing is within this figure. Default 350 mm.Operating surplusExtra cord beyond one finished drop for the pull. Default 150 mm.Fabric roll widthUsed only to warn about joins. Default 1370 mm.Pattern repeat0 for plain fabric. Otherwise the face drop is rounded up to the next repeat.

Planning result

Finished 1090 mm × 1395 mm · 6 folds · face 1.52 m

Finished width: 1090 mm
Finished drop: 1395 mm
Fold count: 6
Fold size: 215 mm
Bottom section: 322 mm
Raised stack (estimate): 72 mm
Face cut width: 1190 mm
Face cut drop: 1525 mm
Lining cut width: 1130 mm
Lining cut drop: 1435 mm
Rods: 6 × 1070 mm
Rings / cord: 24 rings · 13940 mm cord

Recess fit deducts the width and drop clearances from the opening measurements. Headrail thickness is not deducted separately.

Diagrams

The drawings follow the same baseline arithmetic as the numbers. They are planning sketches, not pattern pieces.

Front elevation

Rings sit at every rod and cord column. Fold lines are the rod positions, including the longer bottom section.

Side view of folds

The face hangs flat. Extra fabric is only the documented hems and top allowance.

Cord and ring layout

Rod positions from the bottom hem
Rod	From bottom
1	0 mm
2	322 mm
3	537 mm
4	751 mm
5	966 mm
6	1180 mm

Cord column positions from the left edge
Column	From left
1	80 mm
2	390 mm
3	700 mm
4	1010 mm

Professional job-pack preview

Optional labels below stay in the browser until you print or copy. They are not stored, and they do not create a job in any workroom system.

WorkroomCalc planning sheet

Model workroomcalc-baseline-2026-08-21 · 22 August 2026

Estimate only · not a signed cutting ticket

Client / room: —
Face fabric: —
Lining: —
Headrail: —
Style: standard
Mount: recess
Finished width: 1090 mm
Finished drop: 1395 mm

Cutting list
Piece	Width	Drop	Length
Face fabric	1190 mm	1525 mm	1.52 m
Lining	1130 mm	1435 mm	1.44 m
Headrail / hook-and-loop	1090 mm	—	—
Rods	1070 mm	—	6 rods

Rings: 24. Total cord (planning): 13940 mm. Pull right.

How the estimate is built

Model workroomcalc-baseline-2026-08-21 uses published allowances and school-level geometry. It does not copy a commercial workroom formula. Full constants, algebra and test vectors live in the project document docs/formula-provenance.md.

Finished size equals the opening minus recess clearances, or the exact figures you typed.
Fold count is the drop divided by the target fold size, clamped between 3 and 15. The bottom section is one and a half folds so the lowest panel hangs slightly longer.
Face cut width is finished width plus a side turning on each side. Face cut drop is finished drop plus bottom hem, top allowance, and cascade extra when that style is selected.
Cord columns are placed from each edge inset, then spaced no wider than the maximum column spacing where the cap of eight columns allows.

How to use the Roman blind calculator

Start with a careful width and drop measurement. Select recess fit when your figures describe the opening and you want the calculator to apply small fitting clearances. Select exact fit when your figures already describe the intended finished blind size. The separate roman blind measurement guide explains where to take each measurement and why checking the opening in several places matters.

Choose a standard blind for a flat lowered face, or cascade when you want soft folds to remain visible. Cascade construction consumes extra drop, so its face and lining requirements are larger. The default allowances are deliberately visible and editable: open the allowance panel to match the side turnings, bottom hem, top fixing method, fabric width, pattern repeat and cord layout used for your project.

Read the finished size first, then check the face and lining cut dimensions, rod length, ring count and estimated cord. A pattern repeat greater than zero rounds the face drop up to a complete repeat. If the cut width exceeds the entered fabric-roll width, the result warns that a join may be required. Print the planning sheet only after checking the figures against the fabric supplier, lining, headrail instructions and your own making method.

Common questions

What does this calculator estimate?

It estimates finished size, fold layout, face and lining cuts, rods, rings and cord from the measurements you type. The arithmetic is documented in the methods section.

Is this trade-accurate?

No. The figures are a transparent planning estimate. They are not a workroom cutting ticket and should be checked against fabric, lining, headrail and maker allowances before cutting.

Do I need an account or payment?

No. Calculation and printing stay free. This build has no accounts, checkout, analytics tracker or live payment.