Poster Sizes UK: From A4 to A0 and Which One to Choose

Poster sizes in the UK follow the A-series paper system, the same family of sizes that runs from a sheet of office paper right up to exhibition-scale prints. If you run a shop, cafe, or venue in Belfast and you are ordering poster printing for the first time, the names can feel abstract. A2, A1, A0: which one actually fits your window?

The good news is that the system is logical, and once you know the exact dimensions and one simple rule about viewing distance, choosing becomes straightforward. This guide covers every standard poster size used across Northern Ireland, with measurements in millimetres and practical advice on which size suits which job.

How UK Poster Sizes Work

The A-series starts at A0, the largest standard sheet, and every size below it is exactly half the one above. Cut an A0 sheet across its longer edge and you get two A1 sheets. Cut an A1 in half and you get two A2s, and so on down the scale.

Crucially, every size in the series shares the same proportions. A design built at A4 scales cleanly up to A1 or A0 without stretching or cropping, which makes life much easier when you want the same artwork printed in several formats.

Poster Sizes at a Glance

Here are the exact dimensions for every standard UK poster size, from smallest to largest:

• A5: 148mm x 210mm. Handout territory, better thought of as a large flyer than a poster.
• A4: 210mm x 297mm. Standard office paper size, suits noticeboards and till points.
• A3: 297mm x 420mm. Double A4, and the smallest size that reads as a proper poster.
• A2: 420mm x 594mm. The most popular all-rounder for shop and cafe walls.
• A1: 594mm x 841mm. Serious presence, ideal for windows and event boards.
• A0: 841mm x 1189mm. Roughly a square metre of print, exhibition scale.

The A5 poster size question comes up a lot, so it is worth saying plainly: at 148mm x 210mm, A5 works as a counter card or a handout rather than something you hang on a wall. If you are weighing A5 against other small formats, our guide to A5, A6, and DL flyer sizes breaks down when each one earns its keep.

Which Size for Which Job

A useful rule of thumb: for every metre of viewing distance, go up one A-size. Something read at arm's length can be A4, while something that needs to be read from across the street should be A1 or A0. All of our posters are printed in every size from A5 to A0, so the choice comes down to where yours will hang.

Window posters

For a shop window facing a Belfast street, A2 or A1 is the sweet spot. Passers-by are usually two to five metres away and moving, so your headline has to land in a second or two. An A4 sheet in a window almost always looks lost.

Gig and event posters

The classic gig poster is A3, mainly because it fits the pinboards, cafe walls, and shop counters where these posters actually live. For a bigger event with dedicated display space, step up to A1 for entrance boards and foyer displays.

Shop interiors

Inside a shop or cafe, customers stand close, so A4 and A3 do most of the work: offers, menus, opening hours, and point-of-sale messages. Save A2 for a feature wall where you want one promotion to dominate the room.

Exhibitions and trade shows

Exhibition graphics and conference boards usually call for A0, occasionally A1. At over a metre tall, an A0 print holds its own on a busy stand and stays readable from several metres away.

A1 vs A2 Poster: Which Should You Choose?

This is the comparison we get asked about most, because the two sizes sit either side of an awkward line. A2 (420mm x 594mm) is the safer default for interiors: big enough to be noticed, small enough to frame affordably, and cheap to post in a tube.

A1 (594mm x 841mm) has exactly twice the area, and it earns that extra space wherever viewers are further away or moving past quickly. Windows, venue entrances, and event boards all favour A1.

Here is a practical test: stand where your customer will stand. If you are more than about three metres from where the poster will hang, choose A1. If you are closer than that, A2 will read perfectly well and costs less to print, frame, and ship.

Paper Weights, and Indoor vs Outdoor

For indoor posters, 170gsm silk is the standard choice: strong colour, a flat hang, and a sensible price. Step up to 200gsm or 250gsm if the poster will be handled, reused between events, or displayed unframed where a lighter sheet might curl.

Standard paper posters are not built for rain, and Northern Ireland weather shows no mercy. A paper poster behind glass in your window is fine, but anything fixed outside needs waterproof synthetic media or PVC banner material instead, both of which sit in our wider posters and flexible media range.

If your job is bigger than a standard poster, or you are weighing up banners, foamex, and other rigid options, our large format printing guide walks through the full set of materials and when to use each.

Design Tips for Printing at Scale

Resolution is the thing that catches people out. An image that looks sharp on screen, or printed at A4, can turn soft and blocky at A1 because you are enlarging it four times over.

Aim for 300dpi at final print size for anything up to A2. For A1 and A0 you can usually drop to 150dpi at full size, because nobody reads a poster that big from 30 centimetres away.

• Build your artwork at actual print size, or at half size with the resolution doubled.
• Use vector logos and live text wherever possible, since vectors scale to any size without losing sharpness.
• Add 3mm bleed on every edge and keep text at least 10mm inside the trim line.
• Zoom to 100% and check the corners and any photos before you upload the file.

Our artwork guidelines cover bleed, colour setup, and file formats in more detail if you want to get the file right first time.

Once you know your size, ordering takes a few minutes: pick your dimensions, choose your paper, and upload your artwork. We print posters in every size from A5 to A0 here in Belfast, with free delivery anywhere in Northern Ireland.