A4 vs US Letter: what is the difference?

The exact dimensions

So Letter is about 6 mm wider than A4, and A4 is about 18 mm taller. In everyday terms, a Letter page is a little squarer. A4 is defined by the international standard ISO 216, where the A series starts from an A0 sheet of one square metre and each size is made by halving the one before it. Letter comes from the North American paper convention and is defined in inches.

Those small differences are enough to cause trouble. A document laid out for one size and printed on the other either gets scaled down, which shrinks the text, or clipped at the edges.

Where each size is used

A4 is the standard office paper in most countries, including the United Kingdom, Ireland, most of Europe, India, Australia, New Zealand and much of Africa and Asia. US Letter is the standard in the United States and Canada, and it is also used in Mexico and in parts of Central and South America and the Philippines, though practice varies by organisation.

That means the right choice is decided by who will print or file the document, not by where you are sitting. A UK graduate applying to a US university should send a Letter-sized PDF if it will be printed there; an American applying to a German employer should usually send A4. If the recipient will only read it on screen, the difference matters much less, but a matching page size still looks more professional.

How to choose

1. Read the instructions. If a form, portal or employer specifies a page size, follow it.
2. Think about where it will be printed. Use the standard in the country of the person or office that prints it.
3. When it is read on screen only, use your own country's standard, or whichever the recipient's documents use.
4. When you truly cannot tell, A4 is the more common choice globally, but asking takes ten seconds and removes the guess.

For resumes in particular, the page size should match the country you are applying in. See resume formatting and one page or two for related layout choices.

Choosing the size when you make a PDF

If you build the PDF from photographs or scans, Images to PDF lets you pick A4 or US Letter, set the orientation and choose margins. Each image becomes one page and is fitted within the page and margins in proportion, so nothing is stretched. There is also an option to size pages to the images instead, which follows the source dimensions and is useful when the pages are not meant to be printed on standard paper.

Some practical points:

• Choose the size before you create the PDF. Converting the page size afterwards is not something the tool does.
• A tall phone photo on a Letter page leaves side space, and a wide landscape photo may look better if you switch the orientation.
• Margins around 10 to 15 mm (about half an inch) keep content away from the edge, where many printers cannot print.
• Images become image-based pages, so text is not searchable. For a text document, export a PDF from your word processor at the correct paper size instead.

Setting the size in a word processor

Word processors default to the size matching your region, which is often wrong for the document in front of you. Check the page setup before you start writing, not after, because changing the size later can reflow the text and push a one-page resume onto two pages. In Word, Google Docs and similar programs the setting sits under Page Setup or Layout; choose A4 or Letter from the paper size list. Then export to PDF and check that the page count is what you expect.

If you receive a PDF on the wrong size and just need pages on their own, Split PDF can extract the pages you need, but it does not resize them.

Printing on the wrong paper

Sometimes the paper in the tray decides for you. If you print an A4 PDF on Letter paper, set the printer dialog to "fit to page" or "shrink to printable area". The page shrinks a little and gains slightly wider side margins. Printing a Letter PDF on A4 works in the same way, with a little extra white space at top and bottom. Without scaling, a few millimetres at the edge can be lost.

The loss is usually small, but check the result when the document has content near the edge, such as a letterhead, a table or a signature block. For the same reason, leave generous margins in anything that might be printed on either size.

A note on photos and posters

Paper size is a separate matter from photo print sizes, which use their own conventions such as 4 × 6 in or 10 × 15 cm. For those, see print photo sizes. And if your images are the wrong shape, Crop image helps you trim them before placing them on a page. For how pixels relate to printed size, read image DPI explained.

When your PDF is going to a portal rather than a printer, size matters less than file weight. Check PDF too large to email if the file needs shrinking.

Frequently asked questions

What is the difference between A4 and US Letter?

A4 is 210 × 297 mm. US Letter is 8.5 × 11 inches, or 215.9 × 279.4 mm. A4 is narrower and taller, while Letter is wider and shorter.

Which countries use Letter instead of A4?

The United States and Canada use Letter as the standard. It is also used in Mexico and some Central and South American countries and the Philippines. Most other countries use A4.

Can I print an A4 PDF on Letter paper?

Yes. Choose fit to page or shrink to printable area in the print dialog so nothing is cut off. The text will be slightly smaller.

How do I choose A4 or Letter in a PDF?

Pick the size before you create the PDF. In WORDMIO Images to PDF you can choose A4 or Letter, orientation and margins.