A4 vs US Letter for Sewing Patterns: What Changes and Why
A4 and US Letter are the two standard home printer paper sizes, and they are close — but not the same. A4 measures 210 × 297 mm (8.27 × 11.69 inches); US Letter measures 216 × 279 mm (8.5 × 11 inches). A4 is taller and narrower; Letter is shorter and wider. When printing a sewing pattern at home, the difference affects how many tiles your tiled PDF produces and how the pages stack together — but not the accuracy of the printed pieces, as long as you print at 100% with no scaling.
If you are not yet sure what A0 is or why sewing patterns use large-format files, see A0 vs A4 sewing patterns: which to print and why first.
A4 vs US Letter at a glance
| A4 | US Letter | |
|---|---|---|
| Width | 210 mm (8.27") | 216 mm (8.5") |
| Height | 297 mm (11.69") | 279 mm (11") |
| Portrait orientation | Taller and narrower | Shorter and wider |
| Standard in | UK, Europe, Australia, Japan — most of the world | USA, Canada, Mexico, Philippines |
| International standard | ISO 216 | No ISO equivalent |
| Approx. pages for a tiled A0 pattern* | 48–58 pages | 44–54 pages |
*With a 1 cm overlap and standard printable margins. Exact count varies by pattern dimensions.
Which countries use A4 and which use US Letter?
A4 is defined by ISO 216, the international paper size standard adopted by almost every country in the world. If you are in the UK, anywhere in the EU, Australia, New Zealand, or most of Asia and South America, A4 is your standard home printer paper.
US Letter has no ISO equivalent. It predates the metric system and remains the default in the United States, Canada, and a small number of other countries. Buy a printer in the US and the paper tray is designed for Letter; buy one in the UK and it is designed for A4.
This matters for sewing patterns because the indie pattern market is global. A pattern from a US designer — Cashmerette, Friday Pattern Co, Closet Core — is likely to include a Letter-format tiled version. A pattern from a UK or EU designer — Merchant & Mills, Deer & Doe, Named Clothing — is likely to include an A4 version. If you are printing a pattern designed for the other paper size, see the cross-printing sections below.
Does paper size change how many tiles a pattern produces?
Yes, by a modest amount. Because A4 is 18 mm taller than Letter, each A4 tile captures a slightly taller strip of the original pattern. Because Letter is 6 mm wider, each Letter tile captures a slightly wider strip. The net effect on total page count is usually 5–10 pages for a typical A0 dress or coat pattern.
For most sewists this is not a meaningful difference — you are taping the pages together either way. The practical implication is that if you switch paper sizes mid-project, your existing assembled tiles will not match a new set printed on a different size, so always tile an entire pattern in one paper size before printing.
The overlap margin you choose also affects page count independently of paper size. A larger overlap means more repeated area per tile, which means more total tiles. How to print a PDF sewing pattern at the correct scale covers the overlap setting in detail.
Can I print a US Letter sewing pattern on A4 paper?
Yes — with one firm rule: print at 100%, Actual Size, no scaling. Do not let the printer or PDF viewer rescale the output automatically.
If your printer driver automatically scales a Letter-sized PDF to fit A4 paper, it applies a scale factor of roughly 96–97%, because A4 is narrower than Letter. A bodice that should measure 58 cm at the bust will print at around 56 cm. That is a garment-ruining error that will not be obvious until you cut the fabric.
The fix is the same as always: check the test square on page 1 of your tiled output. Measure it with a ruler — it must read exactly 100 mm. If it reads 97 mm or 98 mm, your printer is scaling the page down to fit. See Why your printed sewing pattern is the wrong size for a step-by-step diagnosis.
If you are printing a pre-tiled Letter PDF on A4 without re-tiling: the content will usually fit within the A4 page (since A4 is taller), but the tile positions and overlap guides were calculated for Letter dimensions and may not align cleanly. Re-tiling the original A0 source file to A4 using TileMyPattern is always the cleaner approach.
Can I print an A4 sewing pattern on US Letter paper?
Yes — same rule applies: 100%, no scaling.
The dimension to watch is height. A4 is 297 mm tall; US Letter is only 279 mm tall — 18 mm shorter. If any tile in an A4 PDF runs content right to the very bottom edge of the page, printing on Letter paper will clip the bottom 18 mm of that tile.
In practice this rarely causes problems, because properly formatted pattern tiles leave a margin of at least 10–15 mm at every edge. But it is worth checking: open the A4 PDF in a viewer, look at the bottom edge of several tiles, and confirm there is a visible white margin before printing on Letter paper.
The correct approach for guaranteed accuracy is to re-tile the original A0 source file to US Letter using TileMyPattern. The tiling engine calculates tile positions directly from the A0 dimensions and maps them cleanly to the Letter printable area, so clipping cannot occur.
Which paper size gives more printable area?
The usable area depends primarily on your specific printer's margins — most home printers leave a border of 4–10 mm on each side that cannot be printed on. Here is how the four sizes supported by TileMyPattern compare with a typical 5 mm margin all round:
| Paper size | Full dimensions | Printable area (5 mm margins) |
|---|---|---|
| A4 | 210 × 297 mm | 200 × 287 mm |
| US Letter | 216 × 279 mm | 206 × 269 mm |
| US Legal | 216 × 356 mm | 206 × 346 mm |
| A3 | 297 × 420 mm | 287 × 410 mm |
A4 gives more vertical printable space per tile, which is useful for long pattern pieces. Letter gives slightly more horizontal space. The practical difference between A4 and Letter is small enough that it rarely matters for pattern tiling.
Legal and A3 both offer significantly more area per tile, which reduces the total page count for a large pattern considerably. If your printer handles Legal or A3 paper, it is worth using — it can cut a 50-page A4 assembly down to 25–30 pages and saves a substantial amount of taping.
Does the test square change between A4 and US Letter?
No. The calibration test square is always 100 mm × 100 mm regardless of the paper size you choose. It appears on page 1 of every tiled output, centred within the printable area, and it is always the same physical size — only the page it sits on changes.
Print that first page, measure the square with a ruler, and confirm it reads exactly 100 mm before printing the rest of the pattern. If it measures correctly, every piece on every tile is dimensionally accurate. The test square is your only reliable verification step — use it every single time, on every pattern, on every paper size.
What should I set in TileMyPattern?
Set the output paper size to match the paper loaded in your printer. If your printer takes A4, choose A4; if it takes Letter, choose Letter. The tiler saves your last-used paper size and overlap settings automatically, so you will not need to change them each session.
If you are printing a pattern originally designed for a different paper size than your printer takes, upload the A0 source file to TileMyPattern and tile it fresh to your paper size. Do not attempt to rescale an existing set of pre-tiled pages — always tile from the A0 source to get clean, correctly proportioned output.
Frequently asked questions
Does it matter which paper size I pick in TileMyPattern?+
Only in terms of page count and tile layout. The real-world dimensions of the printed sewing pieces are identical on A4 and Letter, as long as you print at 100% with no scaling. Choose whichever size matches the paper loaded in your printer.
My pattern says 'print on Letter' but I'm in the UK. What do I do?+
Upload the A0 source PDF to TileMyPattern and set the output size to A4. The tool works from the original A0 dimensions and re-tiles to your chosen paper size. You do not need a Letter-format version — the A0 file is always the source of truth.
Can I mix A4 and Letter pages when assembling a pattern?+
No. Tile positions and overlap coordinates are calculated for one specific paper size. If you mix sizes during assembly, the tiles will not align and seam lines will not match. Always print all tiles for a single pattern on the same paper size in one go.
My printer is in the US but accepts A4. Should I use A4 or Letter?+
Use whichever paper is physically in the tray. If you have loaded A4 sheets and set the tray guides to A4, choose A4 in TileMyPattern. If you are using Letter paper, choose Letter. The printer driver setting must match the physical paper — a mismatch triggers automatic scaling that ruins print accuracy.
Will TileMyPattern remember my paper size preference?+
Yes. The tiler saves your last-used paper size and overlap settings in your browser's local storage. They will be there next time you open the page on the same device and browser, so you only need to set them once.