How to calculate curtain fabric and pricing (the formulas retailers actually use)

If you make or sell made-to-measure curtains and roman blinds, every quote you send is a day of work because you need to calcualte and list everything your potential clients need to knwo: how much fabric they buy, how much of that fabric you'll waste, labour cost, and all the rest like custom features, trimmings, fitting, installation, hardware, accessories etc. Most pricing mistakes happen because one of these gets skipped or estimated instead of calculated. Below is the actual math, with worked examples, so you can check your own numbers against it.

1. How much fabric do you need? (the fullness ratio formula)

Fabric needed (cm) = Track or rail width (cm) x Fullness ratio

Fullness ratio is how much fabric is gathered into the folds relative to the flat track width. It's the single biggest driver of fabric quantity.

Example: a 200cm track at 2.2x fullness = 200 x 2.2 = 440cm of fabric needed, before hems.

The part that catches retailers out: fullness ratio isn't fixed. If your price book or spreadsheet assumes 2x for every order regardless of what the customer actually wants, you're either overcharging on light-fabric orders or losing 15-40% of your fabric cost on full-drape orders. That gap compounds over a year of quotes.

2. Pattern repeat allowance

Extra fabric = Pattern repeat (cm) x (number of drops - 1), added on top of the base fullness calculation.

If the fabric has a vertical pattern that needs to line up across panels, you need extra length per drop to match it - this is separate from fullness and easy to forget in a flat per-meter spreadsheet formula, because it isn't linear with the base quantity.

Worked example: a fabric with a 32cm repeat, ordered as a pair (2 drops), needs roughly 32cm extra to keep the pattern aligned across both panels - more on wider windows with more drops.

3. Wastage allowance

Add 5-8% to your total fabric quantity as standard wastage.

Cutting always produces offcuts, and most fabrics shrink slightly during finishing. If this isn't built into your formula as a percentage, it comes straight out of your margin, order after order, without ever showing up as a line item you can see.

4. Labor by style, not a flat rate

An eyelet curtain and a hand-finished pinch pleat do not take the same time to make. If your business quotes labor as one flat number per meter across your whole catalog, audit your actual hours per style — most retailers who do this find their flat rate underprices at least one style by a meaningful margin.

Putting it together: the full formula

Total price = ((Track width x fullness + pattern repeat) / 100 x fabric price per meter x 1.06 wastage) + Labor + Margin

Use the calculator above to plug in your own track width, fullness ratio, pattern repeat, and fabric price and see the fabric cost update live.

Spreadsheet vs software: what actually changes

If you're quoting from a spreadsheet or price book today, the math above is already running somewhere in your process — the question is whether it runs the same way every time. The two places spreadsheets typically break down:

• Fullness ratio gets treated as fixed even though it should vary by fabric and customer preference, which is where the 15-40% swings above happen.

• Quoting on-site (in a client's living room, without the reference sheet open) is when retailers most often round down instead of recalculating properly — a fast decision under pressure, not a math error.

Software that runs this calculation the same way every time, on any device, removes both failure points without changing anything about how you sell. InterioApp builds fullness ratio, pattern repeat, wastage, and labor-by-style into the quote engine directly. If you sell through Shopify specifically, the same calculation runs as the Curtain and Blind Calculator app, so customers get an accurate instant quote on your store instead of you doing this math manually after they check out.

FAQ

What's the standard fullness ratio for curtains? 2.2x is the most common default for standard drapery. Sheers typically use 1.8x-2x; heavier or blackout fabrics often use 2.5x-3x for a fuller look.

How much wastage should I budget for curtain fabric? 5-8% is a standard allowance for cutting offcuts and minor shrinkage during finishing. Heavily patterned fabric with a large repeat may need more.

Do I need extra fabric for patterned fabric? Yes. Add the pattern repeat length per drop beyond the base fullness calculation so the pattern lines up across panels — this is separate from fullness and often missed in flat pricing.

Why does my curtain pricing keep coming out different from my competitor's? Usually one of these three: a different fullness ratio assumption, no wastage allowance built in, or a flat labor rate that doesn't reflect the actual style being made.