A3 is 297 × 420 mm, which is 29.7 × 42 cm or 11.7 × 16.5 inches. It's twice the size of A4 and half the size of A2. Framed, an A3 print comes out at roughly 34 × 46 cm to 40 × 52 cm on the wall, depending on how wide the frame is.
Below you'll find A3 in every unit you might need, how it compares with the sizes people confuse it with, and how big it actually looks once it's framed and hanging.
In this guide
A3 dimensions in every unit
| Unit | Width × height (portrait) |
|---|---|
| Millimetres | 297 × 420 mm |
| Centimetres | 29.7 × 42 cm |
| Inches | 11.7 × 16.5 in (11.69 × 16.54 to two decimals) |
| Area | 0.125 m², exactly one eighth of a square metre |
Turned sideways (landscape), it's simply 420 × 297 mm. The shape stays the same.
A3 compared with A4, A2 and other sizes
Every A size is exactly half the one above it, and they all share the same shape. That's why a design scales from A4 to A3 to A2 without anything being cropped.
| Size | Millimetres | Compared with A3 |
|---|---|---|
| A5 | 148 × 210 | A quarter of A3 |
| A4 | 210 × 297 | Half of A3 |
| A3 | 297 × 420 | - |
| A2 | 420 × 594 | Twice A3 |
| A1 | 594 × 841 | Four times A3 |
| A0 | 841 × 1189 | Eight times A3 |
A3 is the size of two A4 sheets laid side by side along their long edges. It's a popular size for art prints and posters because it has real presence on a wall without needing a lot of space.
Sizes that look like A3 but aren't
A few common sizes are close enough to A3 to cause mix-ups, but they won't fit an A3 frame properly.
| Size | Centimetres | Difference from A3 |
|---|---|---|
| 11 x 17 inches (US tabloid) | 27.9 × 43.2 | 1.8 cm narrower, 1.2 cm taller |
| 12 x 16 inches | 30.5 × 40.6 | 0.8 cm wider, 1.4 cm shorter |
| 30 x 40 cm | 30 × 40 | 0.3 cm wider, 2 cm shorter |
| A3+ (Super A3) | 32.9 × 48.3 | A printer paper size with room for borders, not a frame size |
An A3 print is too tall for a 12x16 or 30 x 40 cm frame, and an 11x17 poster is too tall for an A3 frame. If you've bought a US poster, check whether it's 11 x 17 before you order a frame. Our picture frame size chart covers the rest of the common sizes.
A3 in pixels, for printing
Pixels depend on the print resolution. For a sharp print, 300 pixels per inch is the usual target; 150 is fine for posters viewed from a distance.
| Resolution | A3 in pixels (portrait) |
|---|---|
| 300 ppi (high quality) | 3508 × 4961 px |
| 150 ppi (posters) | 1754 × 2480 px |
| 72 ppi (screen only) | 842 × 1191 px |
Want to check a specific file? Our pixels to print size calculator tells you how large you can print it.
How big an A3 print looks framed
An A3 frame is named after the print it holds, so the frame itself is bigger by the width of the moulding on every side:
| Moulding width | Outside size of an A3 frame |
|---|---|
| Slim, 20 mm | About 33.7 × 46 cm |
| Medium, 35 mm | About 36.7 × 49 cm |
| Wide, 50 mm | About 39.7 × 52 cm |
On its own, a single A3 frame suits a smaller wall, a hallway, a shelf or the space above a desk. Above a sofa or sideboard it can look a little lost, so A3 prints are often hung in pairs or rows. Three A3 frames in a row with 8 cm gaps come out at about 127 cm wide, which sits well above a standard three-seater sofa.
Which frame for an A3 print?
| The look you want | Frame | Mount border |
|---|---|---|
| Print fills the frame, no mount | A3 frame | None |
| A3 print with a mount | A2 frame | About 6.2 cm at the sides, 8.7 cm top and bottom |
| A3 print with a deep, gallery-style mount | 50 x 70 cm frame | About 10.2 cm at the sides, 14 cm top and bottom |
| A4 print with a mount, in an A3 frame | A3 frame | About 4.4 cm at the sides, 6.2 cm top and bottom |
If you want a perfectly even border all round, our custom-cut mounts can be made to any width.
See it before you buy. On any of our A3 frames, tap Preview Your Own Artwork and upload a photo of your print to see it in the frame. There's more on this in our guide to seeing your artwork in a frame before you buy.
Key takeaways
- A3 is 297 × 420 mm, 29.7 × 42 cm, or 11.7 × 16.5 inches.
- A3 is twice the size of A4 and half the size of A2.
- 11 x 17 inches, 12 x 16 inches and 30 x 40 cm are close to A3 but won't fit an A3 frame properly.
- At 300 ppi, an A3 print needs an image of 3508 × 4961 pixels.
- Framed, A3 is about 34 × 46 cm to 40 × 52 cm on the wall. For a mount, go up to an A2 or 50 x 70 cm frame.
Common questions
How big is A3 in cm?
29.7 × 42 cm.
What is A3 size in inches?
11.7 × 16.5 inches (11.69 × 16.54 inches to two decimal places).
Is A3 bigger than A4?
Yes. A3 is twice the size of A4. Two A4 sheets side by side make one A3.
How many A4 sheets are in an A3?
Two.
Is A3 the same as 11x17?
No. 11 x 17 inches (27.9 × 43.2 cm) is a US size. It's narrower and slightly taller than A3, so the two don't fit each other's frames.
What size frame do I need for an A3 print?
An A3 frame if you want the print to fill it. For a mount around the print, choose an A2 frame or a 50 x 70 cm frame.
What is A3 used for?
Art prints, posters, drawings, small presentation boards, menus and sketchbooks. It's large enough to have impact on a wall but still easy to hang in most spaces.
What size is A3 in pixels?
3508 × 4961 pixels at 300 ppi, which is the usual target for a sharp print, or 1754 × 2480 pixels at 150 ppi.
More framing guides: photo and picture frame sizes, how to hang a picture and how to see your artwork in a frame before you buy.
Browse our A3 picture frames, handmade to order by Guild Certified Framers.
About the author: Trevor Beers
Trevor Beers is a guest writer for East Side Studio London. With two degrees in English language and a passion for contemporary art, he explores the intersections of culture, criticism, and collecting. Splitting his time between London and Austin, Trevor brings an academic eye to emerging art scenes, offering thoughtful perspectives on today's evolving art landscape.
Leave a comment
This site is protected by hCaptcha and the hCaptcha Privacy Policy and Terms of Service apply.