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A pattern repeat is the block of design that repeats across a fabric, and matching it matters whenever a pattern must line up: wallpaper seams, curtain panels, and dress fabric all depend on it. If you ignore the repeat, seams land in the middle of a motif and the eye catches the break instantly. This free tool works out how many repeats fit across your fabric width, how many rows you need, and how much fabric to buy so the pattern stays matched.
Enter the fabric width, the length you need, and the repeat width and height. The tool rounds up to whole repeats across the width and whole rows along the length, because a partial repeat at a seam looks wrong. It then gives the fabric length you must buy, which is the number of rows times the repeat height, and the extra length that matching adds beyond your plain measurement.
A worked example helps. With a fabric 140 centimetres wide, a length of 200 centimetres, and a repeat of 50 by 60 centimetres, you fit three repeats across and need four rows, so you must buy 240 centimetres. The extra 40 centimetres is the price of a matched pattern, and it is far cheaper than a curtain whose flowers jump sideways at every seam.
Half-drop repeats need special care. In a half-drop, each column of the pattern is shifted down by half a repeat, which hides the grid and looks more natural. The tool reports the half-drop offset, which is half the repeat height, so you can mark it when you cut. Half-drops use the same fabric length calculation, but cutting mistakes are easier, so mark every piece before you cut any of them.
Straight matches and half-drops are not the only layouts. Some patterns are random, with no repeat to match, and those need no extra fabric at all. Others are one-way, meaning the motif has a clear up and down, so every piece must be cut the same way up. Check the pattern type before you buy: paying for matching on a random pattern wastes money, and ignoring a one-way direction ruins a dress.
Seam allowances sit outside this calculation. The tool works with finished lengths, so add your seam allowances, hems, and any pattern placement you want, such as centring a large motif on a cushion front, before you compare with the result. Centring a motif can add a whole repeat to a small piece, which is worth knowing before you cut rather than after.
For wallpaper, the same maths applies with rolls instead of metres. Count repeats per roll width, work out drops per roll, and round up, because a short roll cannot be joined invisibly in the middle of a wall. For curtains, remember that both panels of a pair should match each other as well as themselves, which usually means cutting both from the same point in the repeat.
All results here are estimates and guidance only. Real fabric needs vary with the pattern, the cutting layout, and how you place motifs. Use the calculator to buy with confidence, then lay the fabric out and check the match by eye before you cut.
Always buy a little more than the calculator says when the fabric is expensive to reorder or the dye lot may change. One extra repeat length is cheap insurance against a cutting mistake, a stain, or a panel that must be recut because the motif landed badly. For curtains, that extra length also covers the second panel if you cut both from the same point in the repeat and one panel goes wrong. Keep the offcut: it is useful for matching cushions, testing seams, and repairing damage later. Fabric bought today from the same bolt matches perfectly, while fabric bought next month may not, so a small surplus now is worth far more than a perfect calculation later.