What changes from A3 to A1?
A3
297 × 420 mm
A1
594 × 841 mm
Width and height
Twice the linear size
Image detail
Effective PPI halves on enlargement
Image quality, DPI and the finished print size
Enlarging an A3 poster to A1 doubles each dimension and halves photographic PPI. Check the largest image at the final poster size before treating the smaller approved design as production-ready.
Artwork requests often say “DPI”. For photographs, check effective PPI (pixels per inch) at the size actually printed. Printer DPI measures ink or imaging dots and is a different number.
Close-viewed print
Use 300 PPI at finished size as the working target for photographs in leaflets, cards, booklets and similar material. Ask for a quality assessment if the source falls below the agreed specification.
Suitable large-format work
150 PPI at finished size can be a practical starting point for posters or banners viewed from farther away. Close-up detail may need more. Confirm the acceptable minimum for the material, process and viewing distance.
Check the minimum suitable image quality
- Use the best original and calculate effective PPI after cropping and scaling: pixels ÷ printed width in inches. Check both dimensions.
- Inspect for out-of-focus detail, pixelation, blocky JPEG compression and unwanted sharpening. A high resolution number alone cannot make a poor original sharp.
- Keep logos, type, QR codes and fine diagrams as vectors wherever possible. Photographic PPI targets do not define their vector quality.
- Inspect the exported PDF and an actual-size sample, including small text and the largest photograph. Check whether export has reduced image resolution.
Example: 2,400 pixels across 8 inches gives 300 PPI; across 16 inches it gives 150 PPI. Changing a metadata field to “300 DPI” does not restore lost detail. Artwork built at 1:10 scale is enlarged tenfold, so its image PPI is divided by ten at output.
Read the image-resolution guide → Technical references: Adobe resolution guidance · Effective PPI in InDesign
Begin with where it will hang
A poster on a noticeboard, behind a window and on an exhibition wall will be read differently. Measure the available area and check the frame or mounting method. A3 is 297 × 420 mm, A2 420 × 594 mm and A1 594 × 841 mm. Allow for anything the frame hides.
Choose a headline the viewer can understand quickly. Add the event or offer detail in a second level, then the next step. Dates, location and contact details should not compete equally with decorative copy. A poster is usually a poor place to put the whole brochure.
An October hospitality example
Suppose a Warrington venue wants to promote an approved Restaurant Week offer. The organiser's published event dates are 12–18 October 2026. The venue still needs to confirm its own menu, service times, exclusions and any booking requirement. The organiser's announcement does not approve the venue's individual claim.
Make the dates unambiguous and keep the offer readable through the actual glass. If a QR code leads to a menu, check the destination and test the final printed size. Provide a short alternative route as well. A visitor should not need a working phone to understand the basic proposition.
A3 artwork enlarged to A1
Moving from A3 to A1 doubles each linear dimension and quadruples area. Vector text can stay sharp; a raster image's effective PPI halves. Review the source photograph instead of enlarging a low-resolution preview. A sharp logo does not prove that the photograph beside it has enough detail.
Ask for the appropriate bleed, safe area and output format for the chosen production route. Keep important details clear of trimming and frames. If the poster is mounted or laminated, include that finish in the quotation and timetable rather than adding it after approval.
Printing today does not mean displayed today
Work backwards from the point at which the poster must be in position. Include approval, finishing, collection and installation. Same-day enquiries need a file-status and availability check. The site does not promise that every poster can be produced immediately.
For a repeated campaign, retain the editable master and final approved PDF separately. Remove old-date posters from every display point. Keep a list of sizes and quantities by location, so the next update does not depend on someone remembering which frame was used.
Three poster mistakes that a final proof can catch
The first is competing dates: a headline names one day while the small detail still contains last year's schedule. Search the complete file for date references and compare them with the approved source. Do the same for telephone numbers and booking routes. A visually polished proof can make familiar old information easy to overlook.
The second is a contact detail visible only at screen zoom. Print the relevant section at full size and view it at the intended distance. If the call to action becomes illegible, adjust the hierarchy instead of adding another line of text. A poster should make one useful next step clear.
The third is choosing a display position after the material has been ordered. A bright window, exposed outdoor frame or mounting board can change the requirements. Confirm the position and attachment method early. A venue's installation rules may also restrict adhesives or fixings. Production and display should be specified together so a good print is not left waiting for an unsuitable place to put it.
| Poster component | Final approval check |
|---|---|
| Offer or event | Correct headline, dates and conditions. |
| Destination | Working link, readable address or contact route. |
| Physical display | Size, visible area, material and mounting. |
Two questions before ordering
Can an A3 poster be enlarged to A1?
The layout can be enlarged, but image detail, text hierarchy and output requirements need checking at A1 size.
Do you guarantee same-day poster printing?
Availability depends on artwork, quantity, material, finish and the production schedule. Ask for a confirmed assessment.
Sources and what they establish
The linked publishers provide the source facts. The print-buying analysis and worked examples on this page are original. Manufacturer announcements describe industry developments, not equipment ownership at this site.
- Warrington BID: Restaurant Week announcement ↗7 September 2026
- PDF Association member announcement: callas pdfNest ↗4 June 2026
Sources checked 2 October 2026. Source dates are distinct from this article’s publication date. Undated reference pages are identified as references.