Poster Size and Dimension Guide

Updated: 10th April 2025

If you're designing a bold A2 poster for a local event, you need to make sure your get your poster dimensions right. One of the most common questions we get at instantprint is: "What size is A2 in cm?" or "How big is an A3 poster in inches?"

All our poster sizes like A2, A3 and A4 come from the ISO 216 international standard, which defines the 'A' paper series used across the UK and much of the world.

We’ve put together this simple guide to standard poster sizes, including dimensions in both centimetres and inches, practical usage advice and tips on finishes like 250gsm Silk or Waterproof stock. 

• A4 Poster Size
• A3 Poster Size
• A2 Poster Size
• A1 Poster Size
• A0 Poster Size
• 20 x 30 Poster Size
• 40 x 30 Poster Size
• 60 x 40 Poster Size

A4 Poster Size

Dimensions: 21 x 29.7 cm
Millimetres: 210 x 297 mm
Inches: 8.3 x 11.7 in

A4 posters are the smallest standard option but still pack a punch. They're perfect for close-up viewing and work well in settings where space is limited. Easy to print and display, A4 is a go-to for noticeboards, point-of-sale materials and indoor promotions.

While it won’t fill a shop window like an A1 or A2, A4 is great for delivering quick, clear information where people are likely to stop and read.

Popular uses

• Café menus and tabletop displays

• Office or staffroom notices

• Small event flyers or invites

• POS signage in shops or salons

Stock options
Printed on 150gsm, 250gsm or 350gsm Silk, A4 posters are lightweight, affordable and easy to distribute. They're ideal for short-term use or where you need to display lots of individual messages across different locations.

A3 Poster Size

Dimensions: 29.7 x 42 cm
Millimetres: 297 x 420 mm
Inches: 11.7 x 16.5 in

A3 posters are a popular choice when you want something bigger than A4 without taking up too much space. At twice the size of A4, they’re ideal for promoting events, advertising offers in-store, or even creating fun prints for your home or office.

This size is especially useful for indoor displays where you want to catch attention without overwhelming the space.

Popular uses

• Pub or bar event posters

• In-store sales or seasonal offers

• Art prints and home decor

• Small-scale informational signage

Stock options
We print A3 posters on a choice of 150gsm, 250gsm or 350gsm Silk and 220mic or 400mic Waterproof paper. It’s a cost-effective format that still makes a strong impact.

A2 Poster Size

Dimensions: 59.4 x 42 cm
Millimetres: 594 x 420 mm
Inches: 23.4 x 16.5 in

A2 posters are the go-to size when you need to make more of a statement without going full billboard. They’re big enough to grab attention from a distance, making them ideal for shop windows, gig nights, exhibitions or club events.

Whether you're showcasing your brand at a trade show or advertising a weekend special, A2 gives you the impact you're after while still being easy to handle.

Popular uses

• Shop window posters

• Outdoor event promotion

• Club nights and live music gigs

• Conference or exhibition displays

Stock options
Choose from 150gsm or 250gsm Silk for indoor use, or go with 220mic or 400mic Waterproof PVC if you need something weatherproof. These sturdy stocks are perfect for outdoor displays where durability matters.

A1 Poster Size

Dimensions: 84.1 x 59.4 cm
Millimetres: 841 x 594 mm
Inches: 33.2 x 23.4 in

A1 posters are big enough to stop people in their tracks. If you’ve got a new product launch, an event to shout about or just want to get noticed from across the street, A1 is the way to go.

This size works brilliantly on an A-board outside your venue, drawing attention from passers-by and giving your message space to breathe.

Popular uses

• Restaurant menus or café boards

• Grand openings and big announcements

• Outdoor promotions and posters

• Event branding and welcome signs

Stock options
A1 posters are available on 150gsm or 250gsm Silk, ideal for indoor spaces or A-boards with a protective cover. For outdoor use, go with 220 micron or 400 micron PVC for a weather-resistant finish that holds up come rain or shine.

A0 Poster Size

Dimensions: 118.9 x 84.1 cm
Millimetres: 1180 x 841 mm
Inches: 46.9 x 33.2 in

A0 posters are the largest in the standard ‘A’ series and are made to turn heads. Whether you're promoting a charity fundraiser, a local festival or a sporting event, this size is perfect for bold, high-impact messaging that needs to be seen from a distance.

If you're planning something big, this is the format to match the occasion.

Popular uses

• Charity events and fun runs

• Festival and gig listings

• Sports matches and community days

• Oversized venue signage

Stock options
You can print A0 on high-quality 250gsm Silk for indoor use, or on waterproof 220 or 400 micron PVC if you’re going outside. This size works well on fences, railings, large windows or temporary boards.

20 x 30 Poster Size

Dimensions: 76.2 x 50.8 cm
Millimetres: 762 x 508 mm
Inches: 30 x 20 in

Sitting between A1 and 40 x 30 in size, the 20 x 30 poster offers a bold format that’s ideal for eye-catching indoor or outdoor displays. It’s large enough to draw attention in high-footfall areas, but still easy to handle and mount.

This versatile size works particularly well for promotional campaigns and signage that needs to be visible without taking up too much wall space.

Popular uses

• Storefront promotions and posters

• Directional signage

• Event branding or ticket info

• Short-term sales or seasonal displays

Stock options
Printed on waterproof 220 or 400 micron PVC or 250gsm Silk, 20 x 30 posters are built to withstand the elements outdoors or shine on indoor displays.

40 x 30 Poster Size

Dimensions: 101.6 x 76.2 cm
Millimetres: 1016 x 762 mm
Inches: 40 x 30 in

The 40 x 30 poster is a real attention grabber. Often used outdoors, it's perfect when you need your message to reach a wider audience quickly. Whether you're promoting fresher’s week around campus or advertising a housing development roadside, this large format gets seen.

It’s a brilliant choice when you want to scale up your design without going too extreme.

Popular uses

• Student union or university event posters

• Property developments and show home ads

• Outdoor campaigns or temporary signage

• High-traffic venue or roadside placement

Stock options
Available on 250gsm Silk for indoor or covered use, or printed on durable 220 or 400 micron PVC for all-weather conditions. This format is built to hold up and stand out.

60 x 40 Poster Size

Dimensions: 152.4 x 101.6 cm
Millimetres: 1524 x 1016 mm
Inches: 60 x 40 in

The 60 x 40 poster is as big as it gets in most public advertising spaces. This huge format is ideal for high-impact campaigns where visibility is everything. You’ll often see them in bus stops, theatre lobbies or large display stands around town.

If you’re promoting a show, a festival or a film release, this size gives you all the space you need to get creative.

Popular uses

• Theatre or dance show posters

• Film advertising

• Festival line ups

• Large-format city displays

Stock options
Printed on high-quality 250gsm Silk for indoor use, or durable 220 or 400 micron PVC for long-term outdoor placement. This size is made to stand out and weather the elements.

So there you have it – your ultimate guide to poster sizes and stocks. Whether you're going big with a 60 x 40 or keeping it compact with an A4, you’ll find the perfect fit for your message.

With free design templates, next day delivery and a free 10-point artwork check included as standard, it’s never been easier to bring your posters to life. Whatever you’re promoting, we’ve got the tools to help you make it stand out.