How to Calculate Curtain Fabric for a Pattern Repeat

What Is a Fabric Pattern Repeat?

A pattern repeat is the vertical distance after which the same design element reappears on the fabric. It is usually printed on the fabric bolt or listed in the product specification.

Example: a fabric with a 12” pattern repeat has its main motif appearing every 12” down the length of the bolt.

Why it matters for curtains: All panels in a set must start at the same point in the pattern so the design matches across panels when they hang side by side. You cannot start one panel midway through a motif and the next panel at the start of a motif.

This forces you to cut every panel starting at the same repeat position — which creates fabric waste.

Step 1: Find the Pattern Repeat

Look on the fabric bolt for:

• “Pattern repeat: Xin” or “V: Xin” (V = vertical repeat)
• Some fabrics list “H” (horizontal) and “V” (vertical) repeats separately — for curtains, only the vertical repeat matters for cut length
• Some fabrics list “half drop” repeats — see note below

If no repeat is listed, the fabric has no repeat (plain, texture, or random pattern) — no adjustment needed.

Half Drop Repeats

A half-drop repeat means alternating vertical columns are offset by half a repeat. For curtains, treat a half-drop the same way as a full repeat using the vertical repeat distance. Most curtain calculators (including this one) handle half-drops this way.

Step 2: Calculate the Adjusted Cut Length

Raw cut length    = drop + top hem + bottom hem
Adjusted cut length = ⌈ raw cut length ÷ pattern repeat ⌉ × pattern repeat

The ⌈ ⌉ symbol means “round up to the next whole number” (ceiling function).

Example:

• Drop: 90”
• Top hem: 4”, Bottom hem: 6” → raw cut length = 100”
• Pattern repeat: 8”

⌈ 100 ÷ 8 ⌉ = ⌈ 12.5 ⌉ = 13
Adjusted cut length = 13 × 8 = 104"
Waste per panel width: 104 - 100 = 4"

If the raw cut length is already a multiple of the repeat (e.g., 96” with an 8” repeat), no waste occurs — 96 ÷ 8 = 12 exactly.

Step 3: Calculate Total Extra Fabric

Total extra waste (inches) = (adjusted cut length - raw cut length) × total widths
Total extra waste (yards)  = total waste inches ÷ 36

Example continued (6 total widths):

Waste per width = 4"
Total waste = 4 × 6 = 24" = 0.67 yards

A 0.67-yard “penalty” for an 8” repeat on a 6-width pair of curtains — not catastrophic, but real money on expensive fabric.

Worked Example: Large Repeat

Fabric: 18” vertical repeat Project: 80” drop, 4” + 6” hems, 2 panels × 2 widths = 4 total widths

Raw cut length = 80 + 4 + 6 = 90"
⌈ 90 ÷ 18 ⌉ = ⌈ 5.0 ⌉ = 5  (exact multiple — no waste!)
Adjusted cut length = 5 × 18 = 90"

Coincidentally, 90” is exactly a multiple of 18” — zero waste. But if the drop were 82”:

Raw cut length = 82 + 4 + 6 = 92"
⌈ 92 ÷ 18 ⌉ = ⌈ 5.11 ⌉ = 6
Adjusted cut length = 6 × 18 = 108"
Waste per width = 16"
Total waste (4 widths) = 64" = 1.78 yards

On expensive fabric at $15/yard, an 18” repeat could add ~$27 in waste on a modest pair of panels.

Pattern Repeat Waste Table

Base raw cut length = 100”. How much extra each repeat adds:

Bold row = most common repeat size for home furnishing fabric.

How to Minimize Pattern Repeat Waste

1. Buy fabric where the drop is already close to a repeat multiple. If your raw cut length is 98” and the repeat is 6”, adjust your drop by 4” to make cut length 96” (a multiple of 6 — zero waste). Even 2–4” shorter or longer drop can eliminate waste entirely.

2. Avoid very large repeats on many-width jobs. A 24” repeat on a 6-width drawing-room project adds over 3 yards of waste. Consider a smaller-repeat version of the fabric if available.

3. Use offcuts for tie-backs, cushions, or a pelmet. Waste pieces are full-width strips. They’re long enough to use for valances, pelmets, tie-backs, or coordinating cushion covers. For typical whole-room fabric estimates including repeat waste, see Curtain Fabric by Room.

4. Order slightly more and keep the remainder. Fabric is discontinued. If you have leftover from the correct dye lot, you can repair or replace a panel years later. Order 5–10% extra and store it.

Use the Curtain Fabric Calculator — enter the pattern repeat and it adjusts the cut length and total yardage automatically.

See also: Curtain Yardage Formula and How to Measure Windows for Curtains.