If you are planning a poster, a menu-on-a-stand, or a large notice, A3 is often the sweet spot. Big enough to be seen at a glance, small enough to print quickly and mount affordably. This guide explains A3 dimensions, how it compares to A4, typical uses, and how to set up files for clean results. You will also find practical details on printing A3 at JayCee in Galway with nationwide delivery.
A3 Dimensions, Plain and Simple
A3 in millimetres: 297 x 420 mm A3 in centimetres: 29.7 x 42.0 cm A3 in inches: 11.7 x 16.5 inches A3 belongs to the ISO 216 Aseries. Each size keeps the same width to height ratio, 1 to √2, so you can scale up or down without changing proportions. A0 folded in half gives A1, then A2, then A3, then A4. A3 is exactly twice the area of A4.
A3 vs A4, What Changes and What Stays
Shape ratio stays the same, so layouts scale neatly. A3 is 297 x 420 mm, A4 is 210 x 297 mm. A3 is 2x the area of A4 and 1x the orientation step larger. Fold an A3 in half along the long edge to get A4. Quick answers to common comparisons: Is A3 bigger than A4? Yes, twice the area. What letter size is A3? There is no exact US Letter equivalent; Letter is 8.5 x 11 inches, much closer to A4. Is A3 paper Legal size? No, US Legal is 8.5 x 14 inches, smaller and different ratio. Is A3 size 12x18? No, A3 is 11.7 x 16.5 inches; 12 x 18 inches is a separate press sheet size sometimes called SRA3 or Super A3. Is A3 a long size? Not formally; it is a standard ISO size with a tall orientation when used portrait. What size is Super A3? Typically 13 x 19 inches, also known as SRA3 in print workflows. For a quick reference to related formats, see our a3 size guide on the site.
Typical A3 Applications in Ireland
A3 performs well where you need visibility at 1 to 2 metres. Posters for shop windows and community boards Instore notices and health and safety updates Menus on stands and counter displays Academic charts, lab diagrams, presentation boards Event timetables and directional signage Price lists, daily specials, and offers at point of sale If you need larger visibility outdoors or across a room, consider stepping up to larger printed signs; if you only need handouts, A4 is usually enough.
File Setup for Sharp A3 Printing Resolution
Documents, leaflets viewed in hand: 300 dpi at final size. Posters viewed up close, fine detail or small type: 300 dpi minimum, 350 dpi if your file includes small text or line art. Vector logos and text where possible for crisp edges. Bleed and safety Add 3 mm bleed on all sides for full bleed designs. Keep key text and logos at least 5 to 7 mm inside the trim edge. Colour and profiles Export to CMYK with embedded profile; convert spot colours if needed. Avoid overrich black for body text; use 100% K for small text. For deep black areas, a safe rich black is 60C 40M 40Y 100K. Fonts and images Outline or embed fonts. Use high quality PDFs; PDF/X1a or PDF/X4 are reliable.
How to Print A3 at Jaycee
Two simple routes in Galway and nationwide. Selfservice A3 documents: Quick A3 colour or black and white via the instore app. Ideal for essays, handouts, presentations, simple notices. Staff can help if you prefer assistance. Staffassisted A3 posters: For high quality posters on heavier stocks with optional finishing. Supply a printready PDF with bleed if edgetoedge colour is required. Turnaround Standard documents: minutes in store, subject to queue. Posters and mounted pieces: typically 1 to 2 working days; allow 2 to 4 during busy periods. Rush orders accommodated where possible. Ordering and delivery Order online with nationwide delivery across Ireland; free delivery on qualifying web orders over the advertised threshold. Click and collect in Galway is available.If your A3 will be handled frequently or displayed in a window, consider lamination for durability and a wipeclean surface. For free standing displays, mounting to foamex boards or corrieboard adds rigidity.
Sustainable Paper Choices
You can choose recycled stocks or FSC certified papers for many A3 jobs. Options include: 100% recycled uncoated papers for notices and internal posters. Silk or matt coated recycled stocks for colour posters and menus. PVCfree alternatives for selected display materials when suitable. Ask the team for availability and the best choice for your job and budget.
Finishing Options for A3
Lamination in gloss or matt for protection Mounting to Foamex or corrieboard for rigid displays Trimming to bleed, corner rounding on request Drilling for hanging, tape application for window mounting Folding to A4 for mailers or packs, stapling for presentation sets If you are preparing menus or price lists for daily use, laminated menus are a practical choice.
Quick FAQ
What is the A3 size? 297 x 420 mm, 29.7 x 42.0 cm, 11.7 x 16.5 inches.
What size is an A3 poster? Same as A3 paper, 297 x 420 mm; add 3 mm bleed if printing edge to edge.
What size is an A3 photo? The same A3 dimensions; photographic aspect ratios vary, so expect cropping unless you design to A3.
What is an A3? A standard ISO 216 paper size, one step larger than A4.
How to print A3 size? Provide a PDF at 300 dpi with bleed if needed, then use instore selfservice for documents or staffassisted poster printing; online ordering is available with nationwide delivery.
What is better, A3 or A4? Depends on viewing distance and content. A3 is better for visibility in windows or on stands; A4 is better for handouts and filing.
What letter size is A3? No direct match in US sizes; closest in area is 11 x 17 inches called Tabloid, still slightly different.
Is A3 size 12x18? No, that is a larger press sheet; some printers call it Super A3 or SRA3.
Is A3 a long size? No; it is a standard ISO proportion, portrait or landscape.
What size is Super A3? Commonly 13 x 19 inches; also known as SRA3.
Getting Started Today
Bring your PDF on your phone via the app or order online. The team at JayCee can guide you on paper weights, recycled options, and the right finish for your display. If you need a durable window piece, add lamination; if you need a rigid sign, mount to foamex boards. For quick instore notices and handouts, use selfservice A3 colour printing for fast results. Nationwide delivery is available, with Galway collection if you prefer. If you are up against a deadline, call in, and we will do our best to prioritise a rush order subject to workload. Helpful resources on our site: a3 colour printing for fast, high quality A3 documents and posters lamination for added durability on menus and display pieces foamex boards for rigid A3 signs and window displays
Summary A3 measures 297 x 420 mm and scales perfectly from A4 while keeping the same clean ratio. Choose A3 for posters, menus on stands, instore notices, and academic charts viewed at short to mid distance. Set files at 300 dpi with 3 mm bleed and safe margins, export a good PDF, and select finishes that suit how and where you will display the piece. JayCee offers selfservice A3 documents, staffassisted A3 posters, recycled paper options, protective lamination, rigid mounting, nationwide delivery, and Galway collection so you can print with confidence.