A4 is 8.27 by 11.7 inches, the standard page size in most countries outside the United States

An A4 document measures 210 millimeters wide by 297 millimeters tall, which converts to 8.27 inches by 11.7 inches. It is the default page size in Europe, Asia, Australia, and most of the world. If you open a blank document in Google Docs, LibreOffice, or Microsoft Word outside the United States, it will default to A4 unless you change it.

The A-series paper sizes follow a mathematical rule: each size is exactly half the previous one when folded in half along the longer edge. A3 is twice as large as A4. A5 is half the size of A4. This system means a document designed for A4 will scale predictably if you need to print it larger or smaller.

A4 is slightly narrower and taller than the US Letter size (8.5 by 11 inches), which is the standard in the United States and Canada. The difference matters when you are sending documents across borders or printing on equipment set to a different default. A document formatted for A4 will have slightly different margins and page breaks when printed on US Letter paper, and vice versa.

Key Takeaways

  • A4 measures 210 by 297 millimeters (8.27 by 11.7 inches) and is the standard page size in most countries except the United States and Canada.
  • When you create a document in a word processor outside the US, it will default to A4 unless you manually change the page size to US Letter.
  • A4 documents printed on US Letter paper or vice versa will have different margins and may break across pages differently than intended.
  • The A-series sizes follow a consistent ratio, so A4 content scales predictably if you need to enlarge it to A3 or reduce it to A5.

How A4 compares to US Letter and other common sizes

US Letter is 8.5 by 11 inches, making it 0.23 inches wider and 0.7 inches shorter than A4. This small difference adds up: a document with 1-inch margins on all sides leaves 6.5 by 9 inches of usable space on Letter, but 6.27 by 9.7 inches on A4. If you are writing a document that will be printed in multiple countries, choosing one size and sticking to it prevents surprises.

A5 is half the size of A4 (5.8 by 8.3 inches) and is sometimes used for small booklets, notepads, or greeting cards. A3 is twice the size of A4 (11.7 by 16.5 inches) and is common for posters, large diagrams, or technical drawings. Legal size (8.5 by 14 inches) is used in the United States for contracts and formal documents, but is not standard elsewhere.

Why your document editor defaults to A4 or Letter

Document editors set a default page size based on your location and the software's origin. Microsoft Word defaults to US Letter in the United States and Canada, but to A4 in most other countries. Google Docs detects your location from your account settings and defaults accordingly. LibreOffice and other open-source editors often default to A4 globally, since A4 is the international standard.

If you create a document in one country and open it in another, the page size setting travels with the file. A document created on A4 in Germany will remain A4 when you open it in the United States, even if your local default is Letter. This is why you may see unexpected margins or page breaks when you receive a document from abroad.

Changing your page size in common editors

In Microsoft Word, go to the Layout tab, click Size, and choose either A4 or Letter from the dropdown. The change applies to the entire document unless you have set up different sections with different page sizes.

In Google Docs, click File, then Page Setup. A dropdown menu shows the current size. Select A4, US Letter, or another size from the list. The change takes effect when ready and saves automatically.

In LibreOffice Writer, go to Format, then Page. The Page Style dialog opens. Under the Page tab, the Format dropdown shows the current size. Select A4 or Letter and click OK. The change applies to all pages unless you have created multiple page styles.

What happens when you print A4 on Letter paper or vice versa

If you print an A4 document on US Letter paper without adjusting the print settings, the content will scale down slightly to fit, leaving uneven margins. Text near the edges may be cut off if the printer cannot print to the very edge of the paper. Some printers offer a "fit to page" option that shrinks the content automatically, but this can make text smaller than intended.

The safer approach is to change the page size in your document before printing, or to tell your printer to scale the document. Most print dialogs have an option to scale or resize the document to fit the paper size in your printer. Check your printer's manual or help menu for the exact steps, as this varies by printer model.

A4 and document sharing across borders

When you send a document to someone in a different country, mention the page size in your email or cover note if the formatting matters. If you are sending a contract, form, or any document where layout is important, ask the recipient what page size they use and format accordingly. A small note prevents back-and-forth corrections.

For documents that will be read on screen rather than printed, page size matters less. A PDF viewed on a computer or phone will display the same way regardless of the reader's local paper standard. If you are sharing a document that will only be read digitally, you can use either A4 or Letter without concern.

Why A4 became the global standard

A4 is part of the ISO 216 standard, adopted by most countries in the 1970s and 1980s. The A-series system was designed in Germany in the 1920s and offers mathematical elegance: folding an A4 sheet in half produces two A5 sheets, and two A4 sheets side by side equal one A3 sheet. This consistency makes it useful for printing, copying, and scaling documents.

The United States and Canada never adopted the ISO standard, partly because US Letter was already entrenched in business and government before the international standard existed. Today, A4 is used by the United Nations, the European Union, and most international organizations, making it the de facto global standard for formal documents.

Frequently Asked Questions

What is the difference between A4 and US Letter in millimeters?

A4 is 210 by 297 millimeters. US Letter is 215.9 by 279.4 millimeters. A4 is narrower by about 6 millimeters and taller by about 18 millimeters. The difference is small but noticeable when margins are tight or when documents are printed side by side.

Can I change the default page size in my document editor?

Yes. In Microsoft Word, go to Layout, click Size, and select your preferred default. In Google Docs, you can set a default in File > Page Setup, though it applies only to new documents created from that point forward. In LibreOffice, go to Tools > Options > Load/Save > General and set your preferred page format.

Will my A4 document look wrong if someone in the US prints it?

It may have uneven margins or slightly cut-off edges, depending on the printer and print settings. Ask the US recipient to check their printer settings for a "fit to page" or "scale" option, or to change the page size in the document before printing. Most modern printers handle this automatically if you tell them to fit the content to the paper size.

Is A4 the same as A4 landscape?

No. A4 portrait is 210 by 297 millimeters (tall). A4 landscape is 297 by 210 millimeters (wide). Both are A4, but the orientation is different. You can change orientation in your document editor without changing the page size itself.

What page size should I use if I am not sure?

If you are in the United States or Canada, use US Letter. If you are anywhere else, use A4. If you are sending a document internationally, ask the recipient what they use, or save it as a PDF so the formatting stays the same regardless of their printer settings.