A4 at 300 DPI — the print standard
For anything going to a printer — flyers, resumes, magazine pages, photo prints — set your canvas to 2480 × 3508 pixels. 300 DPI is the resolution at which individual dots become invisible at normal reading distance, and it's the default requirement of print shops. If your file will include bleed (art running to the trimmed edge), add 3 mm per side: 216 × 303 mm = 2551 × 3579 px at 300 DPI.
A4 for screens — 72 and 96 DPI
Documents viewed only on screen don't need print resolution. At the classic 72 DPI, A4 is 595 × 842 px — which is also the A4 page size in PDF points, since PDF uses 72 points per inch. At 96 DPI (the CSS reference pixel density) A4 is 794 × 1123 px, which is why many word processors render an A4 page about 794 px wide at 100% zoom. Use these sizes for on-screen mockups, e-signature documents, and web previews of paper documents.
A4 landscape in pixels
Landscape just swaps the two numbers: 3508 × 2480 px at 300 DPI, 842 × 595 at 72, 1754 × 1240 at 150, 7016 × 4961 at 600. Use the orientation selector above and every output — pixels, mm, cm, inches — flips accordingly, along with the visual comparison.
ISO 216 paper sizes chart — A and B series
ISO 216 sizes aren't arbitrary: A0 is defined as one square meter of paper with sides in the ratio 1:√2, and each smaller size is the previous one folded in half with dimensions rounded down to whole millimeters. Because the ratio is √2, halving preserves the shape — this is the only ratio with that property. The table below is computed from that definition (successive halving from A0 = 841 × 1189 mm and B0 = 1000 × 1414 mm), with pixels at 300 DPI. Every row has its own anchor, e.g. #a1 or #b5.
| Size | mm | inches | px @ 300 DPI |
|---|
Which DPI do I need?
Match the DPI to the destination, not to a habit. 300 DPI: professional print, photo books, anything read up close. 150 DPI: home inkjet drafts, internal documents, large posters viewed from a distance (a poster seen from two meters can drop to 100–150 DPI with no visible loss). 72–96 DPI: screen-only documents, email attachments, web images of pages. 600 DPI: line art, small text, technical drawings — continuous-tone photos gain almost nothing above 300, but crisp black-and-white edges do. Higher DPI means bigger files: doubling DPI quadruples the pixel count.
US Letter vs A4
US Letter (216 × 279 mm / 8.5 × 11 in) is slightly wider and shorter than A4 (210 × 297 mm). At 300 DPI, Letter is 2550 × 3300 px against A4's 2480 × 3508 px. A document laid out for one will clip or shrink on the other: printing A4 content on Letter risks cutting the bottom, and Letter content on A4 risks cutting the sides. If a file must print acceptably on both, keep at least 20 mm of margin top and bottom and 8 mm left and right — or design to the shared area of both sheets (210 × 279 mm).
Megapixels to print size
How large can a photo print sharply? Divide the pixel dimensions by the DPI. A 24 MP camera image of 6000 × 4000 px prints at 6000÷300 × 4000÷300 = 20 × 13.3 inches (508 × 339 mm) at full 300 DPI quality — comfortably bigger than A4. At a relaxed 150 DPI (fine for wall art viewed at arm's length or further) it stretches to 40 × 26.7 inches.
Megapixels → max sharp print size
Frequently asked questions
What is A4 size in pixels at 300 DPI?
2480 × 3508 pixels in portrait orientation (3508 × 2480 landscape). It comes from A4's physical size: 210 mm ÷ 25.4 × 300 = 2480 px wide, and 297 mm ÷ 25.4 × 300 = 3508 px tall.
How do I set up an A4 canvas in an image editor?
Create a new document and either enter the physical size directly — 210 × 297 mm with resolution set to 300 pixels/inch — or enter the pixel size 2480 × 3508 px. Both describe the same canvas. If your editor asks for pixels/cm instead of pixels/inch, 300 DPI ≈ 118.11 pixels/cm. Set the color mode to CMYK only if your print shop asks for it; otherwise sRGB is the safe default.
Why do different sites give different pixel answers for A4?
Two reasons. First, DPI: pixels only exist relative to a chosen density, so "A4 in pixels" is meaningless without one — 595 × 842 (72 DPI) and 2480 × 3508 (300 DPI) are both correct answers to different questions. Second, rounding: 210 ÷ 25.4 × 600 = 4960.63, which some sources round to 4961 (this page, direct computation) and others publish as 4960 by doubling the 300 DPI figure. A one-pixel difference is irrelevant in practice, but it explains the inconsistency you'll see.
What is the aspect ratio of A4?
1:√2, approximately 1:1.414. Every ISO 216 size shares it — that's the point of the standard: fold any sheet in half and you get the next size down with exactly the same proportions, so layouts scale between sizes without redesign. No common screen ratio matches it, which is why full-page documents always letterbox on a 16:9 display.