In this article
Choosing a page size for a catalogue, brochure or business document involves more than deciding whether it should look large or small. Content, handling, reading and manufacturing conditions work together. A name such as A4 provides a common reference, but does not explain orientation, folds or production allowances. This guide covers three common sizes and the additional details a useful brief should contain. The dimensions describe finished pages rather than every possible boundary in an output file.
Quick answer
A5 measures 148 × 210 mm, A4 210 × 297 mm and A3 297 × 420 mm. Specify portrait or landscape separately. For folded products, distinguish open and closed dimensions. In production, distinguish the finished trim from any additional bleed or printer-mark area. Include units whenever dimensions are shared or approved.
Write dimensions with their units
Do not send 21 × 29.7 without identifying centimetres or millimetres. State which edge comes first. Use the same dimensions in the quotation and approval file. A standard format name is a helpful starting point, but numerical dimensions and units remove ambiguity when the printer prepares a job or when several teams discuss different output versions.
Decide orientation through actual reading
An A4 landscape page uses the same area differently from a portrait page. Tables, comparisons and short explanations may suit different arrangements. Discuss whether the reader handles the document or consults it on a desk. Try actual content in both orientations instead of choosing purely through an attractive presentation mockup that does not reveal the reading task.
Separate open and folded dimensions
A hypothetical introductory leaflet may close into a small format while opening into a larger surface. State open size, closed size and fold type separately. Review important text against fold positions. Use the production supplier’s template for panel details rather than assuming every panel is automatically equal. A folded specification needs more information than the name of the starting sheet.
Distinguish trim from the wider artwork area
Finished page size describes the result after cutting. Any extra area required for manufacturing should be specified separately. Do not interpret A4 as necessarily including every mark and bleed in a production file. Ask the supplier for requirements, then explain the relevant boundaries in handover notes so a convenient preview is not mistaken for the manufacturing specification.
Use an actual-size trial to assess suitability
Print a hypothetical sales sheet and inspect names, explanations and tables. If a small format repeatedly forces tiny text, revisit the content or size. Larger paper is not automatically better either. Consider carrying and distribution alongside reading. Comparing the same task across formats provides more useful evidence than judging their covers at different zoom levels on a monitor.
Prepare a dimension brief for BOCW
Share the document type, intended reader, approximate content and supplier conditions. A product inventory helps catalogue planning; message priorities help a short brochure. Compare A3, A4 and A5 through the same content task. Confirm production suitability before final approval and record the approved specification. This keeps the design choice connected to a usable physical document rather than only a nominal standard size.
Key takeaways
- A5: 148 × 210 mm; A4: 210 × 297 mm; A3: 297 × 420 mm.
- Specify orientation and open or closed dimensions.
- Keep finished trim separate from additional production space.
- Test reading and handling at actual size before approving a format.
- Record which dimension is width and reconcile inconsistent orientation notes before production.
Frequently asked questions
Does landscape change A4 dimensions?
The edges change orientation: an A4 landscape page can be specified as 297 mm wide and 210 mm high.
Is A3 twice A4?
Its area is twice A4’s area. That does not mean both edge lengths are doubled.
Are these the outer dimensions of every print file?
No. Bleed and printer-mark space may be additional. Confirm the finished trim separately.
