What are the exact dimensions of A4 paper?

A4 is 210 by 297 mm, which is 21 by 29.7 cm, or 8.27 by 11.69 inches. As a pixel canvas it is 595 by 842 px at 72 DPI, 1240 by 1754 px at 150 DPI, and 2480 by 3508 px at 300 DPI. A4 is the worldwide office default everywhere except the United States and Canada, where Letter takes its place.

What is the difference between A4 and US Letter?

A4 (210 by 297 mm) is narrower and taller than US Letter (215.9 by 279.4 mm, or 8.5 by 11 inches). A4 is about 6 mm narrower and 18 mm longer. Documents laid out for one size can clip or leave a strip of margin when printed on the other, so always set the page size to match the printer tray and PDF target.

How many pixels is A4 at 300 DPI?

A4 at 300 DPI is 2480 by 3508 px. The math is the inch size times the DPI: 8.2677 in times 300 rounds to 2480, and 11.6929 in times 300 rounds to 3508. 300 DPI is the standard for press-ready print, so design a flyer or poster at that pixel size and it stays sharp on paper.

How does the ISO A series folding rule work?

Each A size is exactly half the area of the one above it, made by folding the larger sheet across its long edge. Two A4 sheets side by side make one A3 (297 by 420 mm), two A3 make one A2, and so on up to A0, which is one square metre. The aspect ratio stays the same (1 to the square root of 2) at every step, so artwork scales without re-cropping.

What size envelope fits an A5 or A4 letter?

The ISO C series is built to hold A folds. A C5 envelope (162 by 229 mm) fits a flat A5 sheet or an A4 folded once. A C6 (114 by 162 mm) fits an A4 folded twice or a flat A6. A C4 (229 by 324 mm) holds a flat, unfolded A4. Match the C number to the folded size of what you are mailing.

Does DPI change the physical paper size?

No. DPI only changes the pixel count, not the physical sheet. A4 is always 210 by 297 mm whether you export it at 72 or 300 DPI. Higher DPI packs more pixels into the same physical area, which is why a 300 DPI A4 (2480 by 3508 px) prints sharper than a 72 DPI one (595 by 842 px) even though both fill the identical sheet.

Set up a print artboard at the right pixel size

You are starting a flyer in Photoshop or Figma and need the canvas to print on A4 without rescaling. Pick A4, switch DPI to 300, and read 2480 by 3508 px. Type those numbers straight into the new-document dialog and your design fills the sheet edge to edge with no surprise margins when it reaches the press.

Pick the envelope that fits a folded letter

You are mailing an A4 contract and do not know which envelope to buy. The C series holds A folds: a C4 takes a flat A4, a C5 takes an A4 folded once, a C6 takes it folded twice. Look up the C5 dimensions (162 by 229 mm), match them to the box on the shelf, and the letter slides in without forcing.

Translate a US Letter layout to A4 for an overseas client

A client in Europe needs your US Letter document on A4. Put both sheets side by side: Letter is 215.9 by 279.4 mm, A4 is 210 by 297 mm, so A4 is narrower and longer. Knowing the exact gap tells you to pull the side margins in and let the page run taller before you re-export the PDF.

Check that a scan will hit a target resolution

You need a 300 DPI scan of an A4 page for archiving. The tool shows that means a 2480 by 3508 px image. After scanning, compare your file dimensions to that number: if it comes back 1240 by 1754, the scanner ran at 150 DPI and you need to redo it at the higher setting.

Paper Size Reference: A4, Letter, ISO and US in mm, inches, pixels

A4, Letter, A3, B5 and every ISO and US sheet in mm, cm, inches and pixels at 72/150/300 DPI, browser-only

Runs locally
Category Format Converter
Best for Turning pasted content or local files into a handoff-friendly format.

Pick any standard sheet and read it in millimetres, centimetres, inches, and as a pixel canvas at 72, 150, or 300 DPI. Dimensions are shown portrait (short side first). ISO A sizes halve cleanly: fold A3 across its long edge and you get two A4s, so each step down is exactly half the area of the one above.

Choose a paper size

ISO A series

ISO B series

ISO C envelopes

US / North America

JIS B (Japan)

ISO RA (untrimmed)

ISO SRA (raw with bleed)

ANSI engineering

Architectural

Photo prints

Pixel DPI

Print resolution. 72 for screen, 150 for drafts, 300 for press-ready.

A4 · Dimensions

Millimetres

210 × 297mm

Centimetres

21 × 29.7cm

Inches

8.2677 × 11.6929in

Pixels at 300 DPI

2480 × 3508px

Shown portrait. Rotate width and height for landscape.

Fold relationship

A4 is half of A3; two A5 sheets make one A4.

What this tool does

A complete paper size reference for designers, printers and anyone who keeps asking how big A4 actually is. Pick any standard sheet and read its exact dimensions in millimetres, centimetres and inches all at once, plus the pixel canvas you need at 72, 150 or 300 DPI. It covers the full ISO 216 A series (A0 down to A10), the ISO B series, the ISO 269 C envelopes that hold A folds, the North American sizes (Letter, Legal, Tabloid, Ledger, Executive and the half sheets) and the Japanese JIS B series. A4 is 210 by 297 mm, which is 2480 by 3508 px at 300 DPI, and the tool spells out the ISO folding rule so it is obvious that two A4 sheets make one A3. Everything runs in your browser, one click copies the full size block, and the share link reopens the exact sheet and DPI you were looking at. No upload, no tracking, 100 percent client-side.

Tool details

Input: Files + Numbers; The page exposes text boxes, numeric controls, file pickers, or structured inputs depending on the tool.
Output: Live result + Copy + Preview; The result area focuses on usable output, with copy, download, or preview actions when supported.
Privacy: Browser-side processing; The main tool logic does not call an external API, so inputs normally stay in the current tab.
Save / share: Shareable URL state; Key settings are encoded in the URL so another person can reopen the same setup.
Performance budget: Initial JS <= 10 KB; No WASM budget is declared, keeping the tool quick to open on mobile.
Best fit: Format Converter · Designer; Category and role tags drive related tools, internal links, and quick fit checks.

How to use

1. Input

Paste or drop your content into the tool panel.
2. Process

Click the button. All processing is local in your browser.
3. Copy / Download

Copy the result or download to disk in one click.

How Paper Size Reference fits into your work

Use it when the main problem is getting content from one practical format into another.

Conversion jobs

Turning pasted content or local files into a handoff-friendly format.
Previewing a conversion before you use it in a larger workflow.
Cleaning small format mismatches without opening a full editor.

Conversion checks

Try a small sample first when the source format is messy.
Check character encoding, separators, and line endings after conversion.
Keep the source until the converted output has been reviewed.

Good next steps

These links move the current task into a more complete workflow.

Real-world use cases

Set up a print artboard at the right pixel size
You are starting a flyer in Photoshop or Figma and need the canvas to print on A4 without rescaling. Pick A4, switch DPI to 300, and read 2480 by 3508 px. Type those numbers straight into the new-document dialog and your design fills the sheet edge to edge with no surprise margins when it reaches the press.
Pick the envelope that fits a folded letter
You are mailing an A4 contract and do not know which envelope to buy. The C series holds A folds: a C4 takes a flat A4, a C5 takes an A4 folded once, a C6 takes it folded twice. Look up the C5 dimensions (162 by 229 mm), match them to the box on the shelf, and the letter slides in without forcing.
Translate a US Letter layout to A4 for an overseas client
A client in Europe needs your US Letter document on A4. Put both sheets side by side: Letter is 215.9 by 279.4 mm, A4 is 210 by 297 mm, so A4 is narrower and longer. Knowing the exact gap tells you to pull the side margins in and let the page run taller before you re-export the PDF.
Check that a scan will hit a target resolution
You need a 300 DPI scan of an A4 page for archiving. The tool shows that means a 2480 by 3508 px image. After scanning, compare your file dimensions to that number: if it comes back 1240 by 1754, the scanner ran at 150 DPI and you need to redo it at the higher setting.

Common pitfalls

Assuming A4 and US Letter are interchangeable. They are not. A4 is 210 by 297 mm and Letter is 215.9 by 279.4 mm, so a layout built for one prints with clipped edges or extra margin on the other. Always set the document size to the actual target paper, not whichever your software defaulted to.
Confusing DPI with physical size. Changing the DPI does not resize the sheet. A4 stays 210 by 297 mm at any DPI. DPI only sets how many pixels fill that fixed area, so 300 DPI gives a 2480 by 3508 image and 72 DPI gives 595 by 842 for the very same piece of paper.
Mixing up ISO B with Japanese JIS B. They share names but not sizes. ISO B5 is 176 by 250 mm while JIS B5 is 182 by 257 mm, a few millimetres larger. If a printer expects one and you supply the other, the page will not register correctly, so confirm which B standard the job uses.

Privacy

This is a static lookup table. Every dimension, conversion and pixel figure is computed by plain JavaScript in your browser tab from a built-in list of standard sizes. Nothing you select is sent anywhere and there is no logging of which sheets you looked up. The one caveat: the share link encodes the selected paper and DPI in the URL query string, so a link pasted into chat records those two values in the recipient server's access log. The sizes are public standards, so that is harmless here.

FAQ

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Paper Size Reference: A4, Letter, ISO and US in mm, inches, pixels

What this tool does

Tool details

How to use

1. Input

2. Process

3. Copy / Download

How Paper Size Reference fits into your work

Conversion jobs

Conversion checks

Good next steps

Real-world use cases

Set up a print artboard at the right pixel size

Pick the envelope that fits a folded letter

Translate a US Letter layout to A4 for an overseas client

Check that a scan will hit a target resolution

Common pitfalls

Privacy

FAQ

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