Fabric Calculators
Every calculator here answers the same underlying question — how much cloth does this project need — and every one of them answers it the same way: solve the width, solve the length, multiply, then round up to something a shop will cut. What differs between projects is which allowances apply and how the fabric has to be joined.
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Curtain fabric calculator
Track width, drop, fullness and pattern repeat in; metres or yards to buy out, with every allowance adjustable.
Curtain fullness calculator
How many widths each curtain needs at the fullness you want — and what whole widths really gather to.
Pattern repeat calculator
The cut length a repeat forces, what is trimmed from every piece, and what matching the design costs.
Fabric yardage calculator
Piece size, how many, roll width — the length to buy, and the strip you pay for but never cut.
Cushion fabric calculator
Cover size, back opening and piping in; the length to buy and a row-by-row cutting plan out.
Upholstery fabric calculator
An editable panel list instead of a rule of thumb — with the cutting plan and the seams it implies.
Seam allowance calculator
Finished size to cut size — and what a different allowance does to the garment you end up with.
Curtain lining calculator
Lining on its own narrower roll, from the flat width your curtains already need.
Roman blind fabric calculator
Fabric and lining for a flat blind — no fullness, but the repeat still decides the cut.
Curtain heading tape calculator
Tape, hooks and cord for a pair of curtains — and why hooks are not counted on the tape.
Tablecloth fabric calculator
Table plus drop, round or rectangular — and whether turning the cloth loses a seam.
Bias binding calculator
Straight-grain strips or one continuous bias strip from a square, costed side by side.
What every calculator here does the same way
Rounding is always upward. Never to nearest, at any step. Buying 40 cm too much fabric costs a few pounds and goes in the offcuts box; buying 20 cm too little means returning for more from a dye lot that may have sold out. The two errors are not equally bad, so they are not treated equally.
Whole widths, not fractions. Fabric is sold by the width, so a curtain needing 1.6 widths gets 2. The consequence is that you almost always end up with more fullness than you asked for — which looks like a bug until you see the arithmetic, so the figure you actually get is always shown next to the figure you requested.
Allowances are inputs, not constants. There is no single standard for how much fabric a heading or a hem consumes; a London workroom, a US drapery shop and a sewing textbook will give three defensible answers. The defaults below are the middle of the UK range, and every one of them is editable on the calculator that uses it.
| Heading | Heading allowance | Hem | Minimum fullness |
|---|---|---|---|
| Pencil pleat | 15 cm | 20 cm | 2× |
| Pinch pleat | 20 cm | 20 cm | 2× |
| Eyelet | 25 cm | 20 cm | 1.8× |
| Tab top | 12 cm | 20 cm | 1.5× |
| Wave | 15 cm | 20 cm | 2× |
Before you measure anything
Three mistakes account for most of the emails a fabric calculator receives, and all three happen before any arithmetic starts. If a word below is unfamiliar, the glossary defines every term these calculators use.
- Measuring the window instead of the track. A curtain track normally extends 15–20 cm past the glass on each side so the curtains can stack clear of it. Measure what the curtains hang from, not what they cover.
- Measuring the drop from the pole. The finished drop runs from the hook, ring or eyelet position — which sits below the pole — down to the hem. The gap is usually 2–4 cm, which is the difference between a floor-length curtain and one that hovers.
- Trusting the roll width on the label. A fabric sold as 140 cm is often 137–140 cm once the selvedge is trimmed, and "54 inch" is 137.16 cm rather than 140 whatever the bolt end says. If the width matters, measure it.
What is coming
The list is long and the order is decided by what people actually search for: Roman blind fabric, sofa and dining-chair upholstery, cushion covers, quilt backing and binding, bias binding, and elastic length. Adding one is a small job because the page structure and the testing are already built — the work is in getting the maths and the assumptions right. Requests genuinely move things up the list.
Working from a pattern written in other units, or for a different roll width? The conversion tools handle both. The formulas behind every calculator are set out in full on the methodology page.