What is the difference between A4 and US Letter?

A4 is 210 × 297 mm, while US Letter is 216 × 279 mm. Letter is slightly wider but shorter than A4. A4 has a larger total area (about 3.5% more), which can cause formatting issues when printing documents designed for one size on the other.

How does the ISO 216 A-series work?

The ISO 216 A-series is based on a single aspect ratio of √2 (approximately 1:1.414). Each size is half the area of the previous size: A1 is half of A0, A2 is half of A1, and so on. This means folding a sheet in half along its longest side produces the next smaller size with the same proportions.

What is Tabloid paper used for?

Tabloid paper (279 × 432 mm or 11 × 17 inches) is commonly used for newspapers, brochures, posters, and large spreadsheets. It is exactly twice the size of Letter paper and is popular in North America for professional printing and design work.

Paper Size Converter

Compare A-series, B-series, Letter, Legal, and Tabloid paper sizes in mm, cm, and inches.

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Paper Size Reference Table

Size	Category	Dimensions (mm)	Dimensions (inches)	Area (cm²)
A0	ISO A	841 × 1189 mm	33.1 × 46.8 in	9999.5 cm²
A1	ISO A	594 × 841 mm	23.4 × 33.1 in	4995.5 cm²
A2	ISO A	420 × 594 mm	16.5 × 23.4 in	2494.8 cm²
A3	ISO A	297 × 420 mm	11.7 × 16.5 in	1247.4 cm²
A4	ISO A	210 × 297 mm	8.3 × 11.7 in	623.7 cm²
A5	ISO A	148 × 210 mm	5.8 × 8.3 in	310.8 cm²
A6	ISO A	105 × 148 mm	4.1 × 5.8 in	155.4 cm²
Letter	US	216 × 279 mm	8.5 × 11.0 in	602.6 cm²
Legal	US	216 × 356 mm	8.5 × 14.0 in	769.0 cm²
Tabloid	US	279 × 432 mm	11.0 × 17.0 in	1205.3 cm²

Compare Two Sizes

First Size

Second Size

Letter

Visual comparison (not to exact scale)

A4 is

103.5%

the area of Letter

(+3.5% difference)

A4 Area

623.7 cm²

Letter Area

602.6 cm²

Dimensions

A4210 × 297 mm

Letter216 × 279 mm

Understanding Paper Size Standards

Paper sizes around the world follow two main standards: ISO 216 (used in most of the world) and North American sizes (used in the US, Canada, and parts of Mexico). For related design tools, try our aspect ratio calculator when laying out print materials.

ISO 216 — The A-Series

The ISO 216 standard defines the A, B, and C series of paper sizes. The A-series is the most common. It is based on a single aspect ratio of √2 ≈ 1.414 (1:√2). This unique ratio means that when you fold a sheet in half along its longest side, the resulting page has the exact same proportions as the original.

A0 has an area of exactly 1 square meter (841 × 1189 mm).
Each subsequent size (A1, A2, A3…) is half the area of the previous one.
A4 (210 × 297 mm) is the standard for letters, documents, and printing worldwide.

North American Paper Sizes

The United States, Canada, and a few other countries use a different set of paper sizes defined by the American National Standards Institute (ANSI). These sizes do not share a consistent aspect ratio.

Letter (8.5 × 11 in / 216 × 279 mm) is the standard for everyday documents and business correspondence.
Legal (8.5 × 14 in / 216 × 356 mm) is commonly used for contracts and legal documents.
Tabloid (11 × 17 in / 279 × 432 mm) is popular for newspapers, brochures, and large-format printing.

Why Do A4 and Letter Cause Printing Issues?

Because A4 and Letter have different dimensions and aspect ratios, a document formatted for one may not fit correctly on the other. If you are converting between metric and imperial units for other projects, see our metric to imperial conversion guide. A4 is slightly narrower and taller than Letter. When printing A4 documents on Letter paper, content near the bottom may be cut off, while Letter documents on A4 may have extra margins on the sides.

Quick Tip

When designing documents for international audiences, use A4 as the default. Most modern software and printers can scale documents between A4 and Letter, but always check the print preview before sending to the printer.

216×279 mm to Inches: US Letter Explained

The dimensions 216 × 279 millimeters are the exact metric equivalent of US Letter size paper (8.5 × 11 inches). This is the standard paper size for everyday documents, business correspondence, and academic papers in the United States, Canada, and parts of Mexico. If you are designing a document in metric units for a North American audience, 216 mm width by 279 mm height is what you should use.

To convert 216 × 279 mm to inches, divide each dimension by 25.4 (the number of millimeters in one inch): 216 ÷ 25.4 = 8.50 inches, and 279 ÷ 25.4 = 10.98 inches (commonly rounded to 11 inches). The total area is 60,264 mm² or approximately 93.5 square inches. US Letter has a different aspect ratio than A4 (1.294 vs 1.414), which is why documents formatted for one size often need adjustment when printed on the other.

8.5 × 13 Paper Size to cm: Legal and Folio Sizes

The dimensions 8.5 × 13 inches describe US Legal size paper, commonly used for contracts, legal documents, and agreements in North America. Converting to centimeters: 8.5 inches × 2.54 = 21.6 cm, and 13 inches × 2.54 = 33.0 cm. So US Legal is 21.6 × 33.0 cm.

Do not confuse US Legal with Folio size, which is 8.5 × 13 inches in some countries but 8.27 × 13 inches (210 × 330 mm) in others. The table below summarizes the most common named paper sizes with their dimensions in millimeters, centimeters, and inches for quick reference.

Size Name	Width (mm)	Height (mm)	Width (cm)	Height (cm)	Width (in)	Height (in)
A0	841	1,189	84.1	118.9	33.1	46.8
A1	594	841	59.4	84.1	23.4	33.1
A2	420	594	42.0	59.4	16.5	23.4
A3	297	420	29.7	42.0	11.7	16.5
A4	210	297	21.0	29.7	8.3	11.7
A5	148	210	14.8	21.0	5.8	8.3
Letter	216	279	21.6	27.9	8.5	11.0
Legal	216	356	21.6	35.6	8.5	14.0
Tabloid	279	432	27.9	43.2	11.0	17.0

External References

For digital layout calculations, explore our Aspect Ratio Calculator.

Frequently Asked Questions

A4 paper measures 210 × 297 millimeters (8.3 × 11.7 inches). It is the standard paper size for documents in most countries outside North America.

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