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Paper Size Guide & Converter

Compare and convert between A-series, B-series, US Letter/Legal/Tabloid, and photo paper sizes.

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Nested paper size outlines comparing A3, A4, US Letter, and A5 dimensions.A3A4LetterA5297 mm420 mm210 mm
Paper sizes follow geometric ratios that preserve aspect ratio when scaled.

Select Sizes to Compare

ISO A

ISO B

US

Photo

Visual Comparison

A4
Letter
SizeGroupWidth (mm)Height (mm)
A4ISO A210.0297.0
LetterUS215.9279.4

Paper Sizes: ISO, US, and Photo Formats

Paper sizes vary around the world. The ISO 216 standard defines the A-series (A0–A10) and B-series (B0–B10) used in most countries, while the United States and Canada primarily use Letter (8.5 × 11 in), Legal (8.5 × 14 in), and Tabloid (11 × 17 in). These differences matter when sharing documents internationally or preparing files for commercial printing.

The A-series is elegant in its design: each size is exactly half the area of the next larger size, and all sizes share the same aspect ratio (1:√2 ≈ 1:1.414). This means an A3 sheet is exactly two A4 sheets side by side. The US Letter size (8.5 × 11 in) is slightly wider and shorter than A4 (210 × 297 mm ≈ 8.27 × 11.69 in), which causes formatting issues when documents are printed across regions.

Photo paper comes in its own set of sizes: 4×6 in, 5×7 in, 8×10 in, and metric equivalents. When printing photos, it is important to match your document or export settings to the actual paper loaded in the printer to avoid unwanted cropping or white borders. To verify that your printer handles edge-to-edge printing correctly on your chosen paper size, try our Bleed & Borderless test page.

Scaled overlay diagram showing A4, US Letter, A3, and Tabloid paper sizes stacked with dimension labels in both millimetres and inches.Paper Size Comparison (to scale)Common paper sizes overlaid for direct visual comparisonA3TabloidA4US LetterA3297 × 420 mm11.7 × 16.5 inTabloid279 × 432 mm11 × 17 inA4210 × 297 mm8.3 × 11.7 inUS Letter216 × 279 mm8.5 × 11 in
A4 and US Letter are close in size but not interchangeable. A4 is narrower and taller; Letter is wider and shorter.

Related content

Bleed & Borderless Test PageRuler & Dimension Test Page

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Dimensions shown are standard specifications. Actual printable area varies by printer model and margin settings. See our methodology and full disclaimer.

Frequently Asked Questions

What is the difference between A4 and US Letter?

A4 is 210 × 297 mm (8.27 × 11.69 in), while US Letter is 215.9 × 279.4 mm (8.5 × 11 in). Letter is slightly wider but shorter than A4. This difference can cause content to be cut off or margins to shift when printing documents designed for one size on the other.

Which paper size should I use?

Use the standard for your region: A4 for most of the world (Europe, Asia, Australia, South America), US Letter for the United States and Canada. For international documents, design with slightly wider margins so the layout works on both A4 and Letter.

What are points in paper measurement?

A point (pt) is a typographic unit equal to 1/72 of an inch (0.3528 mm). Points are primarily used in print design software like InDesign, Illustrator, and PDF specifications. US Letter is 612 × 792 points, and A4 is approximately 595 × 842 points.

What is the biggest standard paper size?

In the ISO A-series, A0 is the largest at 841 × 1189 mm (33.1 × 46.8 in), about 1 square meter in area. In the US system, Architectural E (36 × 48 in) is a common large format. Printers for these sizes are called wide-format or large-format printers.