Reference library
A3 Paper Size
A3 measures 297 x 420 mm, 29.7 x 42 cm, or 11.69 x 16.54 in. See pixel dimensions by DPI, aspect ratio, bleed setup, comparisons, and related tools.
Last checked: 2026-05-01
How we calculate this
Methodology and source handling
We convert physical sizes to inches, multiply by the selected DPI/PPI value, and round to whole pixels.
Quick answer
Copy-ready answer
A3 is 297 x 420 mm, 29.7 x 42 cm, or 11.69 x 16.54 in. At 300 DPI, A3 is 3508 x 4961 px.
Dimensions and specs
| Millimeters | 297 x 420 mm | |
|---|---|---|
| Centimeters | 29.7 x 42 cm | |
| Inches | 11.69 x 16.54 in | |
| 300 DPI pixels | 3508 x 4961 px | |
| Aspect ratio | 1:1.4141 | |
| Standard family | ISO A Series |
Pixels
Pixel dimensions by DPI
| DPI / PPI | Width | Height | Use |
|---|---|---|---|
| 72 DPI | 842 px | 1191 px | Screen or draft reference density |
| 96 DPI | 1123 px | 1587 px | Screen or draft reference density |
| 150 DPI | 1754 px | 2480 px | Screen or draft reference density |
| 300 DPI | 3508 px | 4961 px | Common high-quality print setup |
| 600 DPI | 7016 px | 9921 px | High-resolution archival or print workflow |
Formula
How to calculate this size
297 mm x 300 PPI = 3,508 px wide.
Use this when the artwork stops at the finished edge.
Add 3 mm per side before calculating pixels when artwork reaches the edge.
Common mistakes
Avoid these a3 paper size problems
A paper size needs a PPI target before pixels mean anything for print.
Portrait and landscape use the same dimensions, but width and height swap in the export.
Paper pages show trim size first; add bleed only when the design prints to the edge.
Calculator
Calculate pixels and bleed
Enter any DPI to calculate the pixel dimensions for this physical size.
Compare
Compare A3 Paper Size
Open a curated comparison or send both sizes into the compare tool with a fragment URL.
Workflow
Use A3 Paper Size in a finished file
Copy the millimeter, centimeter, or inch dimensions for the selected paper standard.
Use 300 PPI for most sharp print exports, or match the printer requirement.
Multiply inches by PPI, then add bleed only when artwork reaches the trimmed edge.
Related
Related pages and tools
Same branch
Nearby pages
FAQ
Common questions
What is the exact A3 size?
A3 measures 297 x 420 mm, 29.7 x 42 cm, or approximately 11.69 x 16.54 in.
What is A3 in pixels at 300 DPI?
A3 at 300 DPI is 3508 x 4961 px when rounded to the nearest whole pixel.
What aspect ratio is A3?
A3 has an aspect ratio of about 1:1.4141 based on its 297 x 420 mm physical dimensions.
Should I add bleed to a A3 design?
For print work, a common starting point is 3 mm bleed on each side, making the document 303 x 426 mm before trimming. Confirm final bleed with your printer.
References
Sources and references
ISO 216 physical dimensions. Pixel values are calculated from millimeters / 25.4 x DPI and rounded to whole pixels.
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ISO 216:2007
Used for ISO A and B series physical paper dimensions.
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W3C CSS Values and Units Module
Used for CSS unit definitions, absolute unit relationships, and CSS px behavior.
Last checked: 2026-05-01