What Is 8.5 x 11 Paper Called? | Letter Size Explained

8.5 x 11 paper is called Letter size, also known as US Letter or ANSI A, and it’s the standard paper size in the United States.

If you’ve ever stood in an office supply aisle or opened a printer dialog box, you’ve seen the dimensions 8.5 x 11 inches. That size is officially called Letter, and it’s the default for most North American printing. Whether you’re printing homework, filing reports, or stocking a home office, understanding exactly what this paper is called—and how it differs from other sizes—saves you from misfed trays and cut-off margins.

What Are The Exact Dimensions Of Letter Paper?

Letter paper measures exactly 8.5 by 11 inches. In metric terms, that’s 215.9 by 279.4 millimeters, often rounded to 216 x 279 mm. The size is also called ANSI A in engineering and technical contexts, referring to the American National Standards Institute’s naming system for paper sizes.

Microsoft’s Style Guide recommends writing the size as 8.5″ x 11″ paper rather than variants like “8.5-by-11-inch” or “8 1/2 by 11-inch.” Using consistent notation matters because even small differences in how you describe the size can lead to confusion in printer settings and document formatting.

How Does Letter Size Compare To A4 Paper?

Letter paper is slightly wider and a bit shorter than A4 paper, which is the standard outside North America. A4 measures 210 x 297 mm (8.27 x 11.7 inches). The practical difference: Letter is about 6 mm wider, while A4 is about 18 mm taller.

This close-but-not-identical relationship causes problems when files created for one size print on the other. Printers often need manual paper-size selection, and mismatching the two can shift margins, scale text unexpectedly, or crop the edges of your document.

If your document is for a US audience, Letter is almost always the correct default. For international distribution, confirm whether A4 is required before sending files to print—this single check prevents most paper-related layout disasters.

Letter Vs. Legal Vs. Tabloid: The US Paper Family

Letter isn’t the only standard size in North America. Two close relatives show up constantly:

• Legal measures 8.5 x 14 inches—the same width as Letter but three inches taller, used for contracts and official documents.
• Tabloid (also called Ledger) measures 11 x 17 inches—twice the width of Letter, used for newspapers, posters, and spreadsheets.

One common mistake is saying “8 x 11” when you mean Letter. That missing half-inch of width is the standard size, and dropping it can lead to paper size mismatches in printer trays and page setup dialogs. Another frequent error is confusing Letter with Legal; while they share the same width, Legal’s extra length changes filing requirements and envelope sizes.

These dimensions are confirmed by Cornell’s paper-size reference and RPI’s standard paper sizes page, both of which list US Letter (ANSI A) at 8.5 x 11 inches. Cornell provides the metric conversion, while Wikipedia’s Letter (paper size) article documents the size’s naming standards and typical use cases across the United States, Canada, Mexico, and the Philippines.

Where Is Letter Size Widely Used And Why It Matters

The Letter format is the default standard for US and North American printers, office copiers, folders, binders, and school paper supplies. It’s used across the United States, and also commonly in Canada, Mexico, parts of Latin America, and the Philippines. When you buy a ream labeled “copy paper” in the US, it’s almost certainly Letter size.

The width-to-height ratio is what makes Letter slightly awkward compared to A4. A4 uses the elegant √2 ratio that scales perfectly when folded or doubled, while Letter’s 1:1.294 ratio is purely a historical holdover. It works well enough in practice, but it’s why international paper trays and US trays don’t swap cleanly.

When you’re setting up a new printer, check whether the driver default is set to Letter or A4. Regional settings on laptops and desktops often default to the locale’s standard size, which means a US-built printer profile might assume Letter even when the paper tray is loaded with something else.

When you’re ready to stock up, choosing the right copy paper matters beyond just size. Weight, brightness, and opacity all affect print quality, and not all 8.5 x 11 paper performs equally across inkjet and laser printers. If you’re comparing options for a home office or a busy household, you can see our tested picks for 8.5 x 11 copy paper before you buy.

A final practical note: printer trays, page setup dialogs, and driver defaults may distinguish Letter from A4, and mismatching them can shift margins or cause scaling and cropping. The fix is always simple—select the paper size that matches what’s physically loaded in the tray. Since Letter is the default in the US, most domestic printing avoids this issue entirely. For the best results, always check the paper size selection before hitting print, especially when opening files created on devices set to international defaults.