A4 paper measures 210 x 297 mm, which is 21 x 29.7 cm or 8.27 x 11.69 inches.
It’s the standard size used across the UK, Europe, and most of the rest of the world for printed documents, letterheads, brochures, CVs, and everyday office paper.
A4 paper dimensions sit in the middle of the international A-series paper range, which runs from A0 down to A10.
This paper size guide covers all the common paper sizes and dimensions you’ll come across in UK print work, how A4 compares to similar formats, and when each size is used.
A4 paper size and dimensions: the exact measurements – By Glasgow printing experts
The dimensions of A4 paper are fixed by an international standard called ISO 216, set by the International Organization for Standardization.
Those exact numbers in every unit:
- A4 paper measures 210 x 297 mm (210 mm wide by 297 mm tall).
- In centimetres, that’s 21 x 29.7 cm.
- In inches, A4 is 8.27 x 11.69 inches (sometimes written as 8.27 x 11.7 inches, or rounded to 8.5 x 11 inches in some informal comparisons, though that’s actually US Letter size).
- A4 has a width to height ratio of roughly 1:√2, which is the aspect ratio that defines the whole A-series.
Paper size dimensions are written width first, height second, in portrait orientation.
An A4 sheet in landscape is still 210 x 297 mm as a single sheet of paper, just turned on its side, so the same sheet of A4 measures 297 x 210 mm when laid out horizontally.
That consistency is one of the reasons the A-series is one of the commonly used paper sizes worldwide for quality paper and professional print work.
The A-series standard paper size range: A0 paper, A1 paper, A2 paper, A3 paper, A5 paper, A6
A4 is part of an A-series paper family that runs from A0 (the largest) down to A10 (the smallest).
Each next size is exactly half the size of the one before, created by folding the paper in half along the longer edge.
One A0 sheet equals two A1 sheets, four A2 sheets, eight A3 sheets, and sixteen A4 sheets.
Fold one A4 in half and you get two A5 sheets, which are the standard size often used to create small booklets.
The dimensions of every commonly used paper size in the A-series, with A0 paper size at the top and A6 paper size at the bottom:
A0 paper size
841 x 1189 mm, or 33.1 x 46.8 inches.
Used for posters and large format printing; A0 paper size is the starting point for the whole series.
A1 paper size
594 x 841 mm, or 23.4 x 33.1 inches.
Common for exhibition boards and large posters; A1 paper size sits just below A0.
A2 paper size
420 x 594 mm, or 16.5 x 23.4 inches.
Used for medium posters and architectural prints; A2 paper size is half of A1.
A3 paper size
297 x 420 mm, or 11.7 x 16.5 inches.
Common for brochures, menus, and presentations; A3 paper size is twice the A4 paper size.
A4 paper size
210 x 297 mm, or 8.27 x 11.69 inches. The standard UK document format.
A5 paper size
148 x 210 mm, or 5.83 x 8.27 inches.
Used for flyers, notebooks, and half-size booklets; A5 paper size is half the A4 paper size.
A6 paper size
105 x 148 mm, or 4.13 x 5.83 inches.
Common for postcards and invitations; A6 paper size is half of A5 size.
Why is A4 that specific size?
A4 was defined back in the 1920s in Germany through a Deutsches Institut für Normung standard. This later became ISO 216 when the International Organization for Standardization adopted it.
Paper is defined at each size so that folding any A-series sheet in half always produces two sheets of the next size down with the same proportions.
That’s why the aspect ratio is 1:√2 rather than a round number; it’s the only ratio where the halved paper keeps the same shape.
The standard was designed to save paper and simplify the whole paper format system.
A business card, a flyer, a letterhead, and a poster can all come from one large sheet cut down without any waste or awkward trimming, because each size nests inside the next.
That efficiency is the reason A4 and its siblings became the widely used paper standard everywhere except the United States and Canada, where Letter size still dominates.
A4 vs Letter size: how A4 and letter size paper compare
The main alternative to A4 is Letter size, the commonly available paper size used in the United States and Canada.
Letter measures 8.5 x 11 inches (216 x 279 mm), which is slightly wider but shorter than A4.
If you’ve ever printed a UK document on US paper or vice versa, you’ll have seen the classic cropping problem.
Text near the edge gets clipped, or leaves a strange margin, because the two paper sizes aren’t quite the same.
A4 and Letter size paper exist for historical reasons.
The US never adopted ISO 216 as a standard, so Letter size stayed dominant across North America.
For UK and European designers working on international print jobs, it’s worth knowing both, because a design built at A4 won’t fit properly on a Letter-sized printer without adjustment.
When to use A4 paper and how A4 paper is used in print
A4 paper is used as the default paper size in almost every UK office, school, and home printer.
When you use A4 paper for a document, you can count on it fitting any standard printer, binder, folder, or envelope without resizing.
Typical situations where A4 is the right size paper to use:
- Letters, letterheads, and official correspondence.
- CVs and cover letters for job applications.
- Reports, essays, and academic documents.
- Flyers and single-sheet marketing pieces.
- Brochures and folded leaflets, either as a full A4 sheet or folded from A4 down to DL or A5.
- Invoices, contracts, and legal paperwork (though legal-size paper exists separately in the US).
At Soapbox, A4 size paper handles most of the day-to-day print work we produce, from menus to marketing collateral.
A4 is the paper fit for most printer trays, most filing systems, and most reader expectations. This is why A4 is the most popular paper format for professional documents in sizes used in the UK.
It’s also the standard size paper for most home and office printer hardware. Any document you need to print lands cleanly without tray adjustment.
A4 size in pixels (for screen and printer use)
If you need to design for print at A4 dimensions but you’re working in a pixel-based application like Photoshop, you’ll need to convert from millimetres to pixels.
The conversion depends on the resolution:
- At 72 DPI (standard screen resolution): A4 is 595 x 842 pixels.
- At 150 DPI (draft-quality print): A4 is 1240 x 1754 pixels.
- At 300 DPI (standard commercial print resolution): A4 is 2480 x 3508 pixels.
- At 600 DPI (high-quality print): A4 is 4960 x 7016 pixels.
For any artwork going to a professional printer, 300 DPI is the minimum.
Designing at 72 DPI will produce a blurry printed result, even if it looks fine on screen.
If you need to print quality paper artwork, set up your document at A4 dimensions and 300 DPI from the start.
Need to print at A4 or any other paper size?
If you need to print anything at A4 or at any other international paper sizes, Soapbox Digital Media is here to help.
Our talented printers can get the right page size for your project, even when the size of the paper measures are unique.
To learn more about our services, give us a call on 0141 429 1356 or drop us a note through our contact page. We’ll be more than happy to talk through what you need and the best paper size and format for the job.
