A4, A5, A3 or A6? Choosing a printed size seems straightforward until you need to prepare a folded brochure, magazine or poster that must fit a display. The format affects the design, readability, folding, paper and production method.
The best-known printing paper sizes belong to the A series defined by ISO 216. B sizes, C envelopes, custom dimensions and press sheets that differ from the final trim size are also used. This guide lists the common measurements and explains how to choose one for a real project.
The key dimensions: A4 is 210 × 297 mm, A5 is 148 × 210 mm and A3 is 297 × 420 mm. These are finished-format dimensions, not necessarily the sheet size the printer needs for production.
A-series paper size table
The following ISO 216 A-series dimensions are shown in millimetres and portrait orientation. For landscape pages, simply reverse the width and height.
| Format | Dimensions in mm | Common uses |
|---|---|---|
| A0 | 841 × 1189 | Plans, posters and large graphics |
| A1 | 594 × 841 | Posters and plans |
| A2 | 420 × 594 | Posters and promotional materials |
| A3 | 297 × 420 | Small posters, fold-outs and graphic documents |
| A4 | 210 × 297 | Documents, magazines, catalogues and brochures |
| A5 | 148 × 210 | Books, notebooks, planners and brochures |
| A6 | 105 × 148 | Postcards, small leaflets and invitations |
| A7 | 74 × 105 | Information cards and small printed pieces |
| A8 | 52 × 74 | Labels and small cards |
| A9 | 37 × 52 | Very small printed elements |
The sequence retains approximately the same aspect ratio. Each size is obtained by halving the previous one, rounded to whole millimetres. An A4 is therefore approximately half an A3, and an A5 half an A4.
Choosing a size for the printed product
Brochures and folded leaflets
A brochure may finish at A4, A5 or A6, but clarify whether the stated size refers to the open or folded piece. An A5 folded leaflet, for example, may start from an A4 sheet depending on the layout and tolerances. Compare formats and finishes through our brochure printing service.
Magazines and catalogues
A4 and A5 are common but not exclusive choices. The format affects the column grid, readability, image size and production cost. The page count, paper weight and binding must also be considered.
Books and notebooks
A5 is used for many books and notebooks, but custom editorial formats are common. Confirm the trim size and inner margins before laying out the pages. For publishing projects, see our book printing options.
Posters and large-format graphics
A3, A2, A1 and A0 are frequent poster sizes. The correct choice depends on viewing distance, location and substrate, not simply on selecting the largest. For larger graphics, banners and rigid materials, consult our large-format printing service.
What is ISO 216?
ISO 216 defines standard paper-size series used in many countries. Series A is the most familiar for documents and publications. Series B provides intermediate sizes, while C formats are used mainly for envelopes and correspondence.
The side ratio of the A series is approximately 1:√2. When a sheet is cut in half parallel to its short side, the resulting format retains almost the same proportions.
Differences between the A, B and C series
| Series | Example | Common use |
|---|---|---|
| A | A4: 210 × 297 mm | Documents and printed products |
| B | B4: 250 × 353 mm | Intermediate formats, publications and specialist uses |
| C | C4: 229 × 324 mm | Envelopes for unfolded A4 documents |
A C4 envelope normally holds an unfolded A4 sheet; a C5 can hold an A4 sheet folded in half. Commercial printing also uses manufacturer-specific and non-standard dimensions.
Finished, open and press-sheet sizes are different
The finished or trim size is the product dimension received by the customer. The open size describes a piece before folding. The press-sheet size is the sheet or substrate required for production, including gripper margins, imposition of several items and other allowances.
Do not design a brochure from its commercial name alone without confirming whether it refers to the open or closed format. Nor should you assume that one A3 sheet can print two A4 pages with bleed and production margins; that depends on the imposition and equipment.
Calculating bleed and file size
An A4 piece measuring 210 × 297 mm with 3 mm bleed on every side requires a document measuring 216 × 303 mm including bleed. Its final trim size remains A4.
This is only an example. Three millimetres is common for many jobs, but the actual value must be confirmed with the printer. In addition to bleed, keep text, logos and essential elements inside a safe margin.
Common mistake: bleed does not mean enlarging the entire design without adjusting its elements. Backgrounds extend beyond the trim edge, while important text remains inside the safe area.
How to choose the right paper size
- Define the product. A poster, magazine and folded brochure require different preparation.
- Consider its use. Include viewing distance, distribution, storage and handling.
- Confirm the finished format. State the exact millimetres and whether the dimensions are open or closed.
- Review the layout. Columns, type size, photographs and margins must suit the chosen format.
- Check the production conditions. The printer will confirm the paper, machine, bleed and folding options.
Remember that sheet size and paper weight are separate properties; GSM describes mass per square metre, not the dimensions.
Frequently asked questions
How large is A4 in centimetres?
21 × 29.7 cm, equivalent to 210 × 297 mm.
Which is larger, A3 or A4?
A3 is larger: 297 × 420 mm compared with 210 × 297 mm for A4.
How many A5 pages fit into A4?
Two A5 formats make approximately one A4. Real production must also allow for trimming, bleed and press-sheet imposition.
What is the difference between A4 and C4?
A4 is a sheet size of 210 × 297 mm. C4 is an envelope size of 229 × 324 mm that can hold an unfolded A4 sheet.
Does paper size affect the printing quote?
Yes. It affects material consumption, imposition, sheet yield and sometimes cutting and finishing. Price is not determined by dimensions alone.
Not sure which format to choose? Tell us the product, quantity and intended use so that the size and production requirements can be assessed before quoting.
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