Quick answer: an A5 poster is 148 × 210 mm (14.8 × 21 cm, about 5.8 × 8.3 in), an A4 poster is 210 × 297 mm (21 × 29.7 cm, about 8.3 × 11.7 in) and an A3 poster is 297 × 420 mm (29.7 × 42 cm, about 11.7 × 16.5 in). Every A size has the same shape (a 1 : 1.414 ratio), and each size up is exactly double the area of the one below. At Posterly Studio UK every individual poster comes in A5, A4 and A3, and almost all also come as a framed A4.
UK poster sizes at a glance
| Size | Millimetres | Centimetres | Inches (approx.) | Aspect ratio | Best for |
|---|---|---|---|---|---|
| A5 (Small) | 148 × 210 mm | 14.8 × 21 cm | 5.8 × 8.3 in | 1 : 1.414 | Desks, shelves, bedside, sets and grids |
| A4 (Medium) | 210 × 297 mm | 21 × 29.7 cm | 8.3 × 11.7 in | 1 : 1.414 | Bedrooms, above a desk, gallery walls, gifts |
| A3 (Large) | 297 × 420 mm | 29.7 × 42 cm | 11.7 × 16.5 in | 1 : 1.414 | Statement piece above a bed, sofa or desk; maps |
| A4 Framed | about 240 × 330 mm outer | about 24 × 33 cm outer (21 × 30 cm picture area) | about 9.4 × 13 in outer | n/a | Ready to hang or stand, no frame shopping |
Useful relationships: two A5s side by side make one A4, and two A4s make one A3. A3 is roughly twice the height and width of A5, so it has four times the area.
Which poster size should I choose?
- A4 if you're unsure. It reads well across a typical bedroom and fits most walls, desks and gift budgets.
- A3 if it's the only thing on that wall, or the design has fine detail (maps, busy fantasy scenes, small text).
- A5 if you're collecting a set or filling a small space such as a shelf, a locker or the wall beside a monitor.
- Framed A4 if you want it on the wall the day it arrives without buying a frame separately.
Best poster size by room and spot
- Desk or shelf: A5, or framed A4 standing up. Small prints don't block monitors or cable runs.
- Bedside wall: A5 or A4. A single A4 at eye level when sitting up in bed works in most bedrooms.
- Above a bed: one A3, or three A4s in a row. A single A5 tends to look lost on a wide headboard wall.
- Above a gaming or work desk: A3 centred, or A4 pairs either side of a monitor. See gaming room poster ideas.
- Above a sofa: A3, ideally as part of a group. A common rule of thumb is to fill around two-thirds of the sofa's width with the whole arrangement.
- Gallery wall: mix A3 as the anchor with A4 and A5 around it. Our gallery wall layouts guide has measured layouts.
- Hallways and small rooms: A4, since you usually view them close up.
Viewing distance: how far away will you be standing?
A rough guide is that a print is comfortable to view from about 1.5 to 2 times its diagonal, and it still reads as a clear image from much further away. The diagonals are about 26 cm for A5, 36 cm for A4 and 51 cm for A3.
- Under 1 m away (desk, bedside, shelf): A5 or A4. Detail is easy to see.
- 1 to 2.5 m away (across a bedroom or study): A4, or A3 for detailed designs.
- Over 2.5 m away (living room, from a sofa or across the room): A3, or a group of smaller prints that reads as one larger shape.
Quick check before ordering: cut or fold paper to the size (two sheets of A4 side by side make A3), tape it to the wall and look at it from where you'll usually be.
The framed A4 option
Choose Medium (A4) Framed on the product page (available on most posters) and your A4 print arrives in a slim black frame:
- Outer size about 24 × 33 cm, picture area 21 × 30 cm (fits A4 at 21 × 29.7 cm)
- Fibreboard frame with a black foil finish
- Clear plastic front, not glass, so it's lighter and safer to post
- Can hang on a wall or stand on a shelf, portrait or landscape
Frames are only included when you pick the framed option. A5 and A3 are sold unframed. For framing them yourself, see how to frame an A4 poster, which also covers A5 and A3 frames.
Paper and print (the same for every size)
Every poster is printed in the UK on 250gsm matte paper. Matte doesn't catch glare the way gloss does, which helps in bright rooms and under ceiling lights. More detail: how we print posters in the UK.
Shipping and delivery
- Free tracked UK delivery on orders £20+ (after discounts). £2.99 under £20
- Dispatched within 1 to 2 working days, then usually delivered 2 to 4 working days after dispatch
- Posters ship flat in bubble envelopes, never rolled
- International shipping is available, with rates calculated at checkout
Returns are accepted within 14 days by post (the customer pays return postage). If a print arrives damaged, email sales@posterlystudio.uk with photos and we'll replace it. Full details are on Shipping & Returns.
Matching size to the type of poster
- Gaming maps: A3, so place names stay readable.
- Minecraft paintings: A4 for singles, A5 for a wall of many paintings. See the Minecraft paintings guide.
- Tarot cards: A5 or A4 in rows and grids. See how to make a tarot card wall.
- Anime, movie and horror posters: A4 as the default, A3 for the main poster in the room.
- Fantasy art: A3 to show the detail.
Poster size FAQ
What size is an A4 poster?
210 × 297 mm, which is 21 × 29.7 cm or about 8.3 × 11.7 inches. It's the same size as a sheet of standard UK printer paper.
What size is an A3 poster?
297 × 420 mm, which is 29.7 × 42 cm or about 11.7 × 16.5 inches. That's twice the area of A4.
What size is an A5 poster?
148 × 210 mm, which is 14.8 × 21 cm or about 5.8 × 8.3 inches. That's half an A4.
What is the best poster size for a bedroom?
A4 suits most bedroom walls and bedside spots. Use A3 for one statement poster above the bed, or A5 for a grid or set.
Is A3 bigger than A4?
Yes. A3 is twice the area of A4. Its short side (297 mm) equals A4's long side.
Do your posters come framed?
Only if you choose the Medium (A4) Framed option, which comes in a slim black frame about 24 × 33 cm with a clear plastic front. All other sizes ship unframed.
Are posters rolled or flat?
Flat. Every poster ships flat in a bubble envelope, so there's no curl to flatten out.
Ready to pick? Browse gaming prints, K-pop & Y2K posters, vintage or every poster. More quick answers are on our FAQ.