Free Live Calculators

Roman Blind Calculator: Fabric, Folds & Rods

Calculate fabric, fold count, and rods for flat and cascade roman blinds. Covers inside and outside mount, lining, and works in cm and inches.

Blind Type
Mount Type

Inside recess width — finished blind will be narrower

From top of batten to bottom of blind when fully lowered

Depth of each fold when raised (typically 10–15 cm)

Target spacing between fold lines (typically 20–30 cm)

Allowances (cm)
Top (batten)
Bottom hem
Side (each)

How to Use This Calculator

  1. 1

    Measure your window

    For inside recess: measure the exact recess width and drop. For outside mount: decide how wide and tall you want the blind to hang — typically 5 cm each side beyond the frame and 15 cm above for the batten.

  2. 2

    Choose blind type and mount

    Select Flat for a smooth-faced blind, or Cascade for permanent fabric loops. Select Inside Recess or Outside Mount — the calculator adjusts the finished width automatically.

  3. 3

    Enter your measurements

    Enter window width and finished drop in your chosen unit (cm or inches). Adjust fold depth and fold spacing if needed (defaults are typical UK / US standards).

  4. 4

    Check fold details

    The calculator rounds to the nearest whole number of sections and shows the actual fold spacing. If you need exactly a specific number of folds, adjust fold spacing until the count matches.

  5. 5

    Read fabric requirement

    Results show face fabric in metres and yards, plus lining if enabled. Cut width and cut length are listed separately for marking and cutting. Order at least 10% extra for safety and shrinkage.

What Each Value Means

Finished Drop (cm or inches)
The visible length of the blind when fully lowered — from the bottom of the batten to the bottom edge of the blind. This is the measurement the blind covers, not the cut length.
Fold Depth (cm or inches)
How deep each fold is when the blind is raised. Each fold creates a horizontal roll of fabric at the top. Deeper fold depth = larger stacks, which look more substantial but use more fabric.
Fold Spacing (cm or inches)
The target distance between fold lines. The calculator divides the drop by this value and rounds to the nearest whole number of sections. The actual spacing shown may differ slightly.
Top Allowance (Batten) (cm or inches)
Extra fabric at the top that wraps over the wooden batten and staples to the back. Standard is 5 cm (2 inches). This fabric is hidden behind the batten when the blind is hung.
Bottom Hem (cm or inches)
Extra fabric at the bottom folded double to form the finished hem. Standard is 10 cm (4 inches) which creates a 5 cm (2 inch) visible hem. Some makers add a rod pocket at the bottom hem for extra weight.

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Frequently Asked Questions

How do I calculate fabric for a roman blind?
Cut length = finished drop + (number of folds × fold depth × 2) + top batten allowance + bottom hem. Cut width = finished blind width + side hems × 2. For a 90 cm wide, 120 cm drop flat blind with 4 folds and 12 cm fold depth: cut length = 120 + (4 × 24) + 5 + 10 = 231 cm.
How many folds does a roman blind need?
Divide the finished drop by your desired fold spacing, then round to the nearest whole number of sections. Sections − 1 = number of folds. For a 120 cm drop with 25 cm spacing: 120 ÷ 25 = 4.8 → 5 sections → 4 folds. Most roman blinds have 3–6 folds depending on drop height.
How many rods does a roman blind need?
One rod per fold line. The number of rods equals the number of folds. A blind with 4 folds needs 4 rods. Rods are inserted in pockets sewn at each fold line on the back of the blind.
What is fold depth on a roman blind?
Fold depth is how deep each fold is when the blind is raised — the height of each stacked fold section. Typical fold depth is 10–15 cm (4–6 inches). Deeper folds give a more substantial stack at the top of the window when the blind is raised.
What is the difference between a flat and cascade roman blind?
A flat roman blind hangs smooth and flat when lowered. When raised, the fabric stacks in horizontal folds at the top. A cascade (hobbled) roman blind has permanent horizontal fabric loops that remain visible even when the blind is fully lowered. Cascade blinds need approximately 50% more fabric per fold.
Should I measure inside or outside the window for a roman blind?
Inside recess: measure the width of the recess and the calculator deducts clearance. Outside mount: measure where you want the blind to hang — above and wider than the window frame. Outside mount gives better light blockage; inside recess gives a cleaner look.
How much extra fabric does lining add to a roman blind?
Lining is cut narrower than the face fabric (no side hem allowance) and shorter (no batten or bottom hem bulk). For a typical lined roman blind, the lining adds roughly 5–10% to material cost — it is significantly cheaper than the face fabric on a per-metre basis.
What fabric width do I need for roman blinds?
Most roman blinds fit within a single 137 cm (54 inch) fabric width. Very wide blinds (over 120 cm finished width) may need to join two widths. The calculator warns you if your cut width exceeds the chosen fabric bolt width.