What is the difference between A4 and Letter size paper?

A4 paper measures 210 x 297 mm (approximately 8.27 x 11.69 inches) and is part of the ISO A series widely used internationally, while Letter size paper measures 8.5 x 11 inches and is standard in the US and Canada.

What are the ISO paper size series?

The ISO paper size system includes the A, B, and C series, with A series being the most common. Each size doubles or halves the surface area as you move between sizes, such as A3 being twice the size of A4.

Why do the US and Canada use different paper sizes than the rest of the world?

The US and Canada use Letter, Legal, and Tabloid sizes due to historical and regional printing and office standards, whereas most other countries follow the ISO system for consistency and international standardization.

What Are the Actual Paper Sizes? Understanding ISO and US Standards

Discover the actual paper sizes used worldwide, including ISO A, B, C series and US Letter, Legal, and Tabloid dimensions for printing and documents.

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Aug 9, 2026

Actual paper sizes vary widely globally, categorized mainly into the ISO (International Standard) A, B, and C series, with A4 (210 x 297 mm) being the most commonly used. The U.S. and Canada typically use Letter (8.5 x 11 inches), Legal (8.5 x 14 inches), and Tabloid (11 x 17 inches). Each series escalates in size, for instance, A3 is twice the size of A4, and so on, enabling scalability and consistency in document production and printing.

FAQs & Answers

What is the difference between A4 and Letter size paper? A4 paper measures 210 x 297 mm (approximately 8.27 x 11.69 inches) and is part of the ISO A series widely used internationally, while Letter size paper measures 8.5 x 11 inches and is standard in the US and Canada.
What are the ISO paper size series? The ISO paper size system includes the A, B, and C series, with A series being the most common. Each size doubles or halves the surface area as you move between sizes, such as A3 being twice the size of A4.
Why do the US and Canada use different paper sizes than the rest of the world? The US and Canada use Letter, Legal, and Tabloid sizes due to historical and regional printing and office standards, whereas most other countries follow the ISO system for consistency and international standardization.

Watch More

For more insights into printing standards and document formats, explore our guides on converting paper sizes and tips for selecting the right paper for your printer. Understanding paper dimensions can streamline your printing and document management processes.

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