The letter and A4 paper sizes both originate from standards that organizations set for consistency when printing and storing documents. While you'll find letter paper used in the United States, most other countries will use the A4 size instead. You'll likely just notice a small difference in the width and height when comparing the A4 paper size vs. letter size.

While the paper is otherwise similar when it comes to how you'd use it for your business, it's still important to understand the different paper-sizing systems, considerations for printing and any special uses.

Understanding North American Paper Sizes

The American National Standards Process, or ANSI, has set some standards for paper sizes that establish specific dimensions and two varying aspect ratios for use in the United States, Canada and Mexico. These standards help ensure that an electronic document in a certain size will print as expected on the same size of paper. The ANSI sizes are labeled alphabetically from smallest to largest as follows:

  • ANSI A: This refers to the letter paper size that runs 8.5 inches wide and 11 inches high and has an aspect ratio of 1:1.2941.

  • ANSI B: Referred to as the ledger paper size, this one is 11 inches wide by 17 inches high. Its aspect ratio is 1:1.5455.

  • ANSI C: Suitable for some signs, this size runs 17 inches wide by 22 inches high. It has a 1:1.2941 aspect ratio.

  • ANSI D: Significantly larger than ANSI C, this poster-sized paper is 22 inches wide and 34 inches high. Its aspect ratio is 1:1.5455.

  • ANSI E: As the biggest paper size per the ANSI standards, this one runs 34 inches wide by 44 inches high and features an aspect ratio of 1:1.2941.

Some other common North American paper sizes don't directly fit the ANSI sizes. For example, there's half-letter paper that is 5.5 inches wide and 8.5 inches high and has an aspect ratio of 1:1.5455. There's also the legal paper size that runs 8.5 inches wide by 14 inches high and has an aspect ratio of 1:1.6471.

Exploring International Paper Sizes

When you look at paper sizes outside of North America, you'll find that they correlate to standards that the International Organization for Standardization, or ISO, has set. Unlike with the ANSI sizes in North America, the different ISO paper sizes will all share the same aspect ratio that is 1:1.4142. The ISO has defined the A, B and C series for sizing, but most common sizes you'll see will fall within the A series. Measured from largest to smallest, some of the most common A-series paper sizes include:

  • A0: This giant paper intended for large posters and signs runs 33.1 inches wide by 46.8 inches high.

  • A1: This poster-sized paper measures 23.4 inches wide and 33.1 inches high.

  • A2: Big enough for displays and notices, this paper size runs 16.5 inches wide by 23.4 inches high.

  • A3: Used often for presentations, A3 paper is 11.7 inches wide and 16.5 inches high.

  • A4: Compared most often to letter paper, this size is 8.3 inches wide by 11.7 inches high.

  • A5: With common uses including books and flyers, this compares to the half-letter paper size and is 5.8 inches wide by 8.3 inches high.

  • A6: Often the size of a postcard, A6 paper runs 4.1 inches wide by 5.8 inches high.

  • A7: Used for small notes, this paper size is 2.9 inches wide by 4.1 inches high.

  • A8: This business-card-sized paper is 2 inches wide and 2.9 inches high.

  • A9: This ticket-sized paper runs 1.5 inches wide by 2 inches high.

  • A10: This tiniest paper works for stamps and is 1 inch wide and 1.5 inches high.

You can find a paper-sizes chart online that can give you a good idea visually of how these A sizes compare with one another. You'll also find that folding a specific paper size in half will give you two sheets of the next size down.

Difference Between A4 and Letter

When comparing the A4 paper size vs. letter paper size, you'll find that the subtle differences in width and length as well as the locales where they're used differentiate the two. North American letter paper is 8.5 inches wide and 11 inches high. In contrast, international A4 paper runs slightly narrower and taller at 8.3 inches wide by 11.7 inches high. This difference results in different aspect ratios for the types of paper.

Even though the differences seem quite small, it's important to acknowledge since it can often impact your business when you go to print something that the creator had made based on the A4 size. Printers in the United States usually have their paper settings configured for the letter size. So, if you try to print an A4 document, for example, your printout may be missing some of the content. In cases where you update the printer settings to try to shrink the document to fit the page, you can end up with some extra borders that may look distracting.

Letter and A4 Paper Uses

Internationally, where A4 paper is the standard size, you'll find it used for most of the same types of business documents for which American companies use letter paper. After all, both sizes are sold as regular typing paper in their locales. However, the small size difference might influence which paper size you use for certain purposes.

Some common ways your business might use either type of paper include:

  • Business letters: Both paper sizes will work well for standard business letters.

  • Magazines and booklets: The A4 paper size is more common for magazines around the world, but you can still print materials like training guides and employee handbooks on letter paper.

  • Catalogs: You can use letter or A4 paper to create product catalogs that you hand out to customers or clients.

  • Resumes: Letter paper will work well for most resumes, but an academic CV should be on A4 paper if possible.

  • Invitations: You can use either regular paper or thicker cardstock of either size to make quick invites for a company event.

  • Posters and signs: Depending on the contents, the slightly taller size may make A4 preferable for small posters and signs hung around the office horizontally.

  • Forms: A4 paper can make it easier to fit the contents of a longer form on a single page for convenience.

  • Reports: You'll find both sizes appropriate for expense reports, proposals, market research, case studies, white papers and other common types of business reports.

  • Business cards: Using thick paper like cardstock, you can use either paper size to make multiple business cards per sheet that you can cut out.

  • Tags: You can save money by not having to buy inventory tags and identification labels if you use either type of paper in cardstock to make tags.

  • Drawings: You'll more often find that drawing paper comes in the A4 size and can work if you need to do a quick sketch of a proposed system or an architectural drawing.

Choosing Your Paper Size

In the end, you'll most likely stick with letter paper for use at North American companies. Not only is this size of paper easiest to find and highly versatile but you'll avoid needing to change the printer settings or wasting paper from printing errors.

However, if you do receive an A4 document and need to print it, you can still find A4 paper online and at office-supply stores. You'll want to check your printer's manufacturer for instructions on changing the paper size to prevent issues. Alternatively, you can use editing software from Adobe InDesign to resize the document to letter size for normal printing on letter paper.