How to print a sewing pattern at full size

The test square is the whole check

Somewhere on the first page of the pattern there is a square, usually 10 × 10 cm or 4 × 4 in, sometimes 5 × 5 cm, with its size printed beside it. It is not decoration and it is not optional. It is the pattern designer telling you: if this comes out of your printer at the size written on it, everything else on these pages is right too.

Print that first page on its own, put a ruler on the paper and measure the square edge to edge. Do it before printing the other forty pages, and long before you put scissors near fabric.

Why patterns come out the wrong size

One setting, in nearly every case: the option called Fit to page, Shrink oversized pages, Scale to fit or Fit to printable area, depending on which program is showing you the PDF. It is on by default almost everywhere, including in browsers, and it exists for a good reason — it stops a document being clipped by the margin your printer cannot reach.

For a document that is helpful. For a pattern it is destructive, because it shrinks the page to fit inside the printable area. On A4 that area is roughly 200 × 287 mm instead of 210 × 297, so the pattern comes out at about 95% and your 100 mm test square measures 95. Five per cent through a bodice is most of a size.

The second cause is a paper mismatch. A pattern laid out for A4 sent to a printer set to Letter, or the other way round, gets scaled to fit even when you did not ask for it — the sizes are close enough that nothing looks obviously wrong, and far enough apart to ruin the fit.

The settings that work

The wording differs between programs; the setting is always the same one.

• Scale: Actual size, 100%, or None. Never Fit, Shrink, or Auto.
• Paper size: the one the pattern was drawn for. If the pattern says A4, the dialog must say A4, and the tray must actually hold A4.
• Turn off any Auto-rotate and centre option. It rarely changes the scale, but it moves the alignment marks off where the pattern expects them.
• Print the first page, check it, and only then send the rest. Patterns run to dozens of pages and a wrong setting costs all of them.

Checking it properly

Use a steel rule or a school ruler, not a fabric tape measure — tapes stretch, and stretch is the exact error you are hunting. Measure the printed square from the outside of one line to the outside of the same line opposite, and measure it in both directions.

Half a millimetre out over 100 mm is fine and is mostly the thickness of the printed line. Two millimetres is not fine: that is 2%, which on a full garment is a size, and it will not be forgiving because the error compounds along every seam.

Measuring both directions matters more than it sounds. A printer that feeds paper slightly fast is wrong on one axis only, and a square that measures 100 mm across and 98 mm down tells you something a single measurement would have hidden.

If the square is the wrong size

First look for the cause, because scaling is a fix for the symptom and it will only hold if the cause is genuinely the printer. If the paper size is wrong, correct that and print again — do not paper over it with a scale factor.

If the settings are right and the square is still short, correct it with a ratio: divide the size the square should be by the size it actually is, and multiply by 100. A square that should be 100 mm and measures 95 gives 100 ÷ 95 = 1.053, so print again at 105%. Then measure the square again, because you are correcting one rounding error with another.

If the two directions are out by different amounts, no single scale factor can fix it. That is a paper-feed problem, not a scaling one; check the paper size setting first, then the tray guides, then try a different feed path if your printer has one.

Joining the pages

Tiled patterns come with their own alignment system: triangles, circles, or a letter-and-number grid printed in the margins. Match those marks, never the paper edges. The edges are where your printer stopped, which is not the same place on every sheet.

Trim along the printed trim line on two sides of each page — usually the top and the left — and lay each sheet over its neighbour so the marks sit on top of each other. Tape from the back so nothing catches under a rotary cutter later. Work along a whole row first, then join the completed rows to each other; building outward from the middle lets small errors accumulate somewhere you cannot correct them.

Patterns that come as one large sheet

Many designers ship both a tiled A4 or Letter version and a single A0 copy shop file. If you only have the A0, you can tile it yourself rather than paying for a large-format print — that is what the Poster tool does, and the same 100% rule applies to every tile it produces.

Set the poster size to the true size of the A0 page, 841 × 1189 mm, rather than to a percentage. Then print the tiles at Actual size, exactly as above, and measure the test square on whichever tile carries it before assembling the rest. Tiling a pattern is described in more detail in the guide to printing a poster at home.