Paper Size Guide & Converter
Compare and convert between A-series, B-series, US Letter/Legal/Tabloid, and photo paper sizes.
Last updated
Select Sizes to Compare
ISO A
ISO B
US
Photo
Visual Comparison
| Size | Group | Width (mm) | Height (mm) |
|---|---|---|---|
| A4 | ISO A | 210.0 | 297.0 |
| Letter | US | 215.9 | 279.4 |
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.
Worked examples
Real conversions this tool produces — enter the inputs to reproduce each result.
A4 in every unit a print job asks for
Input
- Size
- A4 (ISO A)
Result
- Millimetres
- 210 × 297 mm
- Inches
- 8.27 × 11.69 in
- Points
- 595 × 842 pt
595 × 842 pt is the value to hand a PDF or InDesign setup — points are what layout software actually uses. A4's 1:√2 ratio means folding it in half gives A5 with the same proportions.
US Letter, for comparison
Input
- Size
- Letter (US)
Result
- Millimetres
- 215.9 × 279.4 mm
- Inches
- 8.50 × 11.00 in
- Points
- 612 × 792 pt
Letter is wider than A4 (8.50 vs 8.27 in) but shorter (11.00 vs 11.69 in) — so a design centred for one leaves uneven margins on the other. Always confirm the target before exporting for an international print run.
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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.
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