Art Paper Sizes: A Simple Framing Cheat Sheet

Confused about A3, 30 x 40, or 50 x 70, and which frame each needs? Use this simple cheat sheet to match prints, frames, and mounts in minutes, without doing mental maths. It covers the most common art paper sizes used in the UK and Europe, plus how they relate to popular US frame sizes.

The two rules that make framing easy

• Match the aspect ratio first, then pick the size. If the proportions are different, you will need a mount with a custom window or you will crop the art.
• Decide if you will use a mount. A mount, also called a mat, makes the frame larger. Outer frame size equals print size plus the mount on all sides.

Aspect ratio families you will see most often:

• A-series family, constant proportion of 1 to √2. Examples are A5, A4, A3, A2, A1. These enlarge or reduce perfectly between sizes.
• 2 to 3 family, examples include 30 x 45 cm, 60 x 90 cm, and 24 x 36 in.
• 4 to 5 family, examples include 40 x 50 cm, 8 x 10 in, and 16 x 20 in.
• 3 to 4 family, examples include 30 x 40 cm and 18 x 24 in.
• Square family, equal sides such as 30 x 30 cm.

If you already know the size you want, browse size-led collections like A3 posters, A2 posters, and 50 x 70 cm posters. If you prefer a ready solution, explore our framed prints, or simply shop all posters.

Quick reference: ISO A‑series paper sizes

The A‑series is defined by the ISO 216 standard. Measurements below are exact in millimetres and centimetres, with inches rounded for convenience.

Tip: A‑series frames are widely available in the UK. If your print is A3, an A3 frame fits edge to edge, no mount required.

Popular metric poster sizes and families

These cover the majority of European frames you will find on the high street and online.

US frame sizes you may encounter in the UK

It is increasingly common to see US‑sized frames in UK shops, especially 24 x 36 inches. Knowing the match helps you avoid near misses.

Note: A “24 x 36 in” frame is not identical to a “60 x 90 cm” print. It is a touch larger, so you would need a correctly cut mount or a 24 x 36 in print to avoid gaps.

Mount maths, made simple

Outer frame size equals print size plus twice the mount width. Keep the sum in a standard frame size for an easy purchase.

Practical tip: It is normal to make the bottom mount 5 to 10 mm thicker than the top. This optical tweak keeps the art looking visually centred once hung.

Safe pairings that just work

• A3 print into A3 frame, no mount, tidy and minimal.
• 30 x 40 cm print into 40 x 50 cm frame with a 5 cm mount, balanced and classic.
• 40 x 50 cm print into 50 x 70 cm frame with a custom mount window, elegant and easy to find.
• 50 x 70 cm print into 70 x 100 cm frame with a 10 cm mount, bold statement.
• 60 x 90 cm print into 70 x 100 cm frame with a 5 cm mount, streamlined and modern.
• 24 x 36 in frame with a 60 x 90 cm print will need a custom mount, do not rely on edge fit.

Picking size for your space

• Desk, sideboard, or hallway niche, choose A3 or 30 x 40 cm. Use a mount to add presence without overpowering the space.
• Over a console or fireplace, try A2 or 50 x 70 cm. A pair hung side by side also works well.
• Over a sofa or bed, aim for a single large piece like 60 x 90 cm or a triptych of A2 or 50 x 70 cm. As a rule of thumb, art should be about two thirds the width of the furniture.
• Tall narrow wall, use portrait 40 x 50 cm or 50 x 70 cm to echo the architecture.

If you already know the size you want, jump straight to A2 posters, A3 posters, or go bigger with 50 x 70 cm posters. Prefer a done‑for‑you solution? See our framed prints.

Common pitfalls to avoid

• Mixing aspect ratios. A 30 x 40 print will not fill a 40 x 50 frame without a mount, there will be gaps or cropping.
• Confusing frame size with window opening. Many frames have a small lip that covers 2 to 3 mm of the print edge. Check the mount window size, not only the frame label.
• Overlooking US sizes. A 60 x 90 cm print in a 24 x 36 in frame needs a mount cut to the right window.
• Forgetting how much larger mounts make the piece. Measure the wall and nearby furniture before picking a mount width.
• Buying before measuring. Measure the space, then pick the ratio and size that suits. Your eye is the final judge, but numbers save returns.

How this translates when shopping at dreamprint.art

• Most artworks offer multiple size options so you can match your preferred frame family without compromising the composition.
• If you want a plug‑and‑play result, choose artworks available as framed versions. Framing options vary by artwork and size, and are a convenient way to get a ready‑to‑hang piece delivered.
• Browsing by size is quick. Explore A3 posters, step up to A2 posters, or make a statement with 50 x 70 cm posters. You can also shop all posters to mix styles and sizes.

One‑minute decision flow

• Choose the wall and how bold you want to go, subtle, balanced, or statement.
• Pick a ratio family that repeats across the set, A‑series, 4 to 5, or 2 to 3, for cohesion.
• Decide on a mount. None for a crisp, modern feel, 5 to 10 cm for a gallery look.
• Select the size and frame pairing from the tables above, then order with confidence.

Sources

• The A‑series is defined by the ISO 216 standard, the basis for paper sizes in the UK and most of Europe.
• Common North American frame sizes are listed under North American paper sizes, useful when a frame label is in inches.

Frequently Asked Questions

Is A3 the same as 30 x 40 cm? Not quite. A3 is 29.7 x 42.0 cm, which is taller and slightly narrower than 30 x 40 cm. Use an A3 frame for A3 art, or a 40 x 50 frame with a custom mount window if you want a mounted look.

What size print fits a 50 x 70 cm frame? A 50 x 70 cm print fits edge to edge. If you want a mount, a 40 x 50 cm print with a 5 cm mount on all sides fits nicely into a 50 x 70 cm frame.

Is 60 x 90 cm the same as 24 x 36 inches? They are close but not identical. 24 x 36 in is roughly 61 x 91.5 cm, a little larger. Use a mount cut to your exact print size when combining these.

How wide should my mount be? For mid‑sized prints like A3 or 30 x 40 cm, 4 to 6 cm looks balanced. For A2 or 50 x 70 cm, 5 to 8 cm. For larger pieces, 8 to 12 cm. Slightly heavier at the bottom looks visually centred on the wall.

Which sizes are best for a small flat? A3 and 30 x 40 cm are versatile and easy to place. Use mounts to add presence without overwhelming the room. For a hero piece, A2 or 50 x 70 cm works well.

Do I need to match the frame orientation to the art? Yes. Portrait art looks best in portrait frames, and landscape art in landscape frames. Square art can go either way.

Do you offer framing? Framing options are available on selected artworks and sizes. If you prefer ready to hang, explore our framed prints.

Ready to find the perfect fit? Explore by size with A3 posters, step up to A2 posters, or make an impact with 50 x 70 cm posters. If you want to browse everything in one place, start with shop all posters.

Get Inspired: Posters to Frame

Now that you know how to match paper sizes to frames, here are some beautiful posters from our collection that would look stunning framed:

Kitchen Poetry Follow the Rainbow by Christina Heitmann

Kitchen Poetry Shapes & Shadows by Christina Heitmann

Victorian Violet by Christina Heitmann

Bubbles by Christina Heitmann

Victorian Vivvi by Christina Heitmann

Looking for more inspiration? Browse our Garden posters collection for nature-inspired designs, or explore our City posters collection for urban artwork that brings metropolitan energy to your walls.