How to Calculate Fabric for Cascade Roman Blinds

What Makes Cascade Different

A cascade (hobbled) roman blind looks different from a flat roman blind even when fully lowered. Instead of hanging flat, the fabric forms permanent horizontal loops — called cascades or hobbles — that are visible at all times.

These loops are sewn into the blind permanently, not created by the raising mechanism. The blind still raises and lowers normally; the loops just gather and stack more when raised.

The Cascade Fold Formula

The fold count is calculated the same way as for flat blinds:

Sections = round(finished drop ÷ fold spacing)
Folds    = sections − 1

The difference is in how much extra fabric each fold requires:

Flat roman:

Extra per fold = fold depth × 2

Cascade roman:

Extra per fold = fold depth × 3

Why 3× instead of 2×?

In a flat blind, each fold stacks behind the face. The fold fabric goes backward one fold depth and returns — 2× total.

In a cascade blind, each fold loops forward, hangs down, and returns. The loop protrudes from the face of the blind:

• Part 1: Fabric goes backward to the fold back point (1× fold depth)
• Part 2: Fabric comes forward and hangs down as the visible loop (1× fold depth)
• Part 3: Fabric returns to the blind face at the next fold line (1× fold depth)

Total = 3× fold depth per fold.

Complete Cascade Calculation

Example: Cascade blind, inside recess

Inputs:

• Window width: 90 cm
• Finished drop: 120 cm
• Fold depth: 12 cm
• Fold spacing: 25 cm
• Top allowance: 5 cm
• Bottom hem: 10 cm
• Side hem: 2.5 cm each

Width:

Finished width = 90 − 2 = 88 cm  (inside recess clearance)
Cut width      = 88 + 2.5 + 2.5 = 93 cm

Length:

Sections        = round(120 ÷ 25) = 5
Folds           = 4
Fold allowance  = 4 × 12 × 3 = 144 cm
Cut length      = 120 + 144 + 5 + 10 = 279 cm = 2.79 m

Compare to flat roman (same window):

Fold allowance (flat) = 4 × 12 × 2 = 96 cm
Cut length (flat)     = 120 + 96 + 5 + 10 = 231 cm = 2.31 m

Cascade uses 48 cm (0.48 m) more fabric than flat for this blind. On a 120 cm drop with 4 folds, cascade adds about 20% to fabric cost.

Fabric Use Comparison: Flat vs Cascade

54” (137 cm) fabric, 12 cm fold depth, standard allowances:

Bold = most common blind size.

Fold Depth for Cascade Blinds

Cascade blinds are commonly made with shallower fold depths than flat blinds — because the loops are permanently visible, smaller loops look neater and less bulky.

Bold = most common choice.

Smaller fold depth = less extra fabric, less cascade drama. Larger fold depth = more fabric, deeper loops.

Fabric Requirements: Cascade vs Other Styles

Budget implication: A cascade blind for a standard bedroom window typically costs 20–30% more in face fabric than a flat roman blind of the same dimensions. For pre-calculated tables by window size, see Roman Blind Fabric Yardage by Window Size. For fabric type guidance, see Best Fabrics for Roman Blinds.

Lining for Cascade Blinds

Lined cascade blinds are common — lining adds body and helps the loops hold their shape.

Lining cut dimensions for cascade:

Lining width  = finished width − 2 cm (0.8")
Lining length = drop + cascade fold allowance + 2 cm (0.8")
             = 120 + 144 + 2 = 266 cm (for the example above)

The Roman Blind Calculator calculates both face and lining cut sizes when you select the lining option.

Use the Roman Blind Calculator to calculate cascade fabric — select “Cascade / Hobbled” as the blind type.

See also: Roman Blind Types Guide and Roman Blind Fabric Formula.