A4 (210 × 297 mm, 8.27 × 11.69 in) is narrower and taller than US Letter (8.5 × 11 in, 216 × 279 mm). A sewing pattern made for one size prints correctly on the other only if each page's content fits inside the smaller sheet; if not, the printer either crops the edges or shrinks the page to fit, and a shrunken pattern no longer fits you. The safe approach is to print a file made for your paper, at 100% ("Actual size"), and to measure the test square before printing the rest.
How do A4 and US Letter compare to other paper sizes?
| Paper | Millimeters | Inches | Where it is common |
|---|---|---|---|
| A4 | 210 × 297 | 8.27 × 11.69 | Europe and most of the world |
| US Letter | 215.9 × 279.4 | 8.5 × 11 | United States, Canada, parts of Latin America |
| A3 | 297 × 420 | 11.69 × 16.54 | Office printers outside North America |
| Tabloid (Ledger) | 279.4 × 431.8 | 11 × 17 | Office printers in North America |
| A0 | 841 × 1189 | 33.1 × 46.8 | Copy shops outside North America |
| Copy shop 36 × 48 in | 914 × 1219 | 36 × 48 | Copy shops in North America |
The difference between A4 and Letter looks small: Letter is about 6 mm (1/4 in) wider and 18 mm (3/4 in) shorter. On a pattern, those millimeters are exactly where the alignment marks and the edges of pieces often sit.
Can you print an A4 pattern on US Letter paper, or the reverse?
Sometimes. An A4 page printed on Letter loses about 18 mm of height, so anything in the top or bottom margin, such as page numbers, alignment marks or the edge of a pattern piece, may be cut off. A Letter page printed on A4 loses about 6 mm of width. Whether that matters depends on how close to the edge the designer placed the content.
What you must never do is let the printer fit the page to the paper. Shrinking an A4 page onto Letter scales it to about 94%, which takes 6 cm (2 3/8 in) off a 100 cm (39 1/2 in) hip. That is more than a full size. The post on why the test square matters shows how small scaling errors add up.
Some designers solve the problem with a single file whose content fits within both sizes, about 198 × 267 mm (7.8 × 10.5 in) of drawing area, and others offer separate A4 and Letter files. If a pattern offers both, always download the one for your paper.
How does Sewly handle A4 and US Letter?
Sewly generates the PDF for the paper you choose, so nothing is cropped or scaled. Each page keeps a margin of about 1 cm (3/8 in) on every side, which any home printer can print without borderless mode: the drawing area is 19 × 27.7 cm on A4 and about 19.6 × 25.9 cm (7.7 × 10.2 in) on Letter. The pieces are arranged to use as few pages as possible on that paper, in portrait or landscape, whichever needs fewer.
Pages are named by row and column (A1, A2… B1), with alignment marks on every shared edge, and the cover has a page map and the test square: a solid 5 cm square and a dashed 2 in square. If you move country or print at work on a different size, download the PDF again for that paper rather than printing the old file. More on Sewly's print options.
As an example, in one test with a T-shirt drafted for a 92 cm (36 in) bust with the default options, the A4 file had 11 pattern pages and the US Letter file 12, while A3 needed 6. The exact count depends on your measurements and options.
Which printer settings print a pattern at the right size?
Whatever the paper, these settings decide whether the pattern prints true to scale:
- Choose the right paper in the print dialog (A4 or Letter), matching the paper in the tray.
- Set the scale to 100%, "Actual size" or "None". Turn off "Fit to page", "Shrink oversized pages" and "Fit to printable area".
- Print from a PDF reader if your browser's print dialog does not offer an actual-size option. Adobe Acrobat Reader and macOS Preview both do.
- Turn off borderless printing. It enlarges the page slightly so it bleeds off the edges.
- Print the page with the test square first and measure it with a ruler before printing the rest.
The full walkthrough is in how to print a PDF sewing pattern at the right scale.
Is it worth printing on A3 or Tabloid instead?
If you have access to an A3 or Tabloid printer, yes. Each sheet holds about twice the area of A4 or Letter, so a pattern needs roughly half as many pages and far fewer joins, and every join is a place where small errors creep in. Many office printers handle A3 or Tabloid, and some home inkjets do too.
For large patterns like trousers or a circle skirt, a copy shop file is easier still: the whole pattern on one or two large sheets, with no taping at all. The guide to printing at a copy shop explains how to order it.
How do you assemble pages from either paper size?
The method is the same for A4 and Letter. Lay the pages out in rows following the page map, trim the margins the pattern tells you to (on Sewly patterns, the dashed edge on two sides of each page), match the alignment marks and tape. Work row by row, then join the rows together, checking the marks rather than the paper edges, as the guide to assembling a tiled PDF pattern shows. A large table or a clean floor makes the job much faster than working page by page on a small desk.