How to check your printer prints at 100 % scale

To check that your printer prints at 100 %, print only the page that carries the test square with scaling set to "actual size" or "100 %", then measure the square with a ruler in both directions. It should read exactly 5 cm (2 in on an inch square). If it is short or long, the fault is almost always a "fit to page" or "shrink to printable area" option in the print dialog, or a mismatch between the PDF page size and the paper in the tray. Fix the setting, reprint the one page, measure again, and only then print the whole pattern.

What do you need to check printer scale?

• The PDF pattern, opened in a dedicated PDF reader rather than a browser tab.
• One sheet of the paper you will use for the whole pattern.
• A ruler or tape measure with clear millimeter or 1/16 in marks. A metal ruler is best; a plastic school ruler is fine; a printed paper ruler is not, because it has the same problem you are trying to detect.
• Two minutes. The check costs one sheet and saves a whole pattern.

How do you check the print scale, step by step?

1. Open the PDF in a PDF reader. Browser previews and some mail apps print with their own scaling and ignore the file's size. Any PDF reader on a computer or tablet gives you a proper print dialog.
2. Find the test square. It is usually on the first pattern page or the page map. On a Sewly pattern the cover carries a 5 cm and a 2 in square so you can check with either ruler.
3. Set the paper size to match the file. An A4 file onto A4 paper, a Letter file onto Letter paper. If they differ, the printer will often scale to fit without telling you. A4 vs US Letter explains why patterns come in both.
4. Set scaling to "actual size", "100 %" or "none". Turn off "fit to printable area", "shrink oversized pages" and "choose paper source by PDF page size". Each printer driver names these differently; look for anything with "fit", "shrink" or "scale" in it.
5. Print only the test page. Type the single page number in the page range field.
6. Measure the square in both directions. Lay the ruler along the top edge of the square from the outer edge of one line to the outer edge of the other, then along the left edge. Printers feed paper in one direction, and an error can show in only one of the two.
7. Compare. A 5 cm square that measures 5.0 cm in both directions passes. Anything 1 mm (1/32 in) or more off is a scaling problem, not a measuring error.
8. If it is off, change one setting and reprint the test page. Do not print the rest hoping the first page was an exception.
9. Print the whole pattern, then spot-check. Measure the square again on the first page of the batch, and measure the width of a page in the middle. Some printers change behavior when the tray is nearly empty or the paper warms up.

How much does a small scaling error matter?

More than it looks. The error applies to every piece in every direction, so it adds up around the body.

The common "fit to page" shrink on a Letter file printed on A4 is about 94 to 96 %. It turns a garment with 6 cm (2 3/8 in) of ease into one with none. The test square exists to catch this, and why the test square matters shows what it looks like in a finished garment.

What are the common mistakes when checking scale?

• Measuring from the inside of one line to the outside of the other. Lines have width. Measure the same edge on both sides: outer to outer or inner to inner.
• Checking only one direction. A printer that is right side to side and 2 % short in the feed direction will pass a one-direction check and stretch every piece into a slightly wrong shape.
• Trusting the "100 %" label in a browser. Browser print dialogs apply margins and can scale a page to fit them. Use a PDF reader.
• Reading the square at an angle. Look straight down at the ruler, with the zero line on the edge of the square, not the end of the ruler.
• Printing double-sided or in booklet mode. Both can trigger scaling and both make the pages unusable for tiling anyway.
• Forgetting the test after a driver update or a new printer. Settings reset. Make the one-page check a habit at the start of every pattern.
• Accepting a 1 mm error as "close enough". On the square it is 2 %, which is 2 cm on a hip.

Note: Draft or economy print quality is fine for patterns and does not affect scale. Toner saving changes the darkness of the lines, not their position.

What if the square still prints wrong?

Try the pattern from a different PDF reader; some readers apply scaling of their own. Check the printer's own settings panel, where a "scale to fit" or "auto-fit" option may be set at the printer level and override the computer. If the square is correct in one direction and wrong in the other, the paper may be slipping on worn feed rollers, and the fix is cleaning or a service rather than a setting.

As a last resort, if the error is consistent and you cannot remove it, compensate: a square that prints at 4.8 cm needs the file printed at 104 % (100 ÷ 96) to come out right. Enter that as a custom scale, print the test page again, and confirm it measures 5.0 cm before you continue. The full print routine, including assembling the pages afterward, is in how to print a PDF sewing pattern at the right scale.

When should you check scale somewhere other than at home?

The test applies anywhere a pattern is reproduced, not only on your own printer.

• At a copy shop, measure the square on the A0 or 36 × 48 in sheet before you pay and leave. Shop software has the same fit-to-page defaults as home printers, and a plotter on a roll can be set to a slightly different width. Printing at a copy shop lists what to tell the counter.
• With a projector, there is no printing, so the check becomes calibration: project the grid, measure a 5 cm or 2 in square on the table, and adjust the zoom until it is exact. Re-check whenever the projector or the table has moved.
• On a photocopy of a paper pattern, copiers also scale by default. Copy a page with a known dimension and measure it.

If you have inherited a stack of already-printed pages with no test square, measure the printed page margin or the width of the tiled page frame against the figures in the pattern's instructions, or reprint the first page only and compare it with the old one laid on top. Other errors that creep in at the printing stage, such as mixed paper sizes or a rotated page, are collected in PDF pattern printing mistakes that ruin the fit.