A3 is a popular paper size used for posters, artwork, photography and design prints. If you're planning to frame an A3 piece, it's important to understand both the dimensions of the paper and the options available when it comes to framing. A3 frames come in a range of styles and formats, from exact-fit frames to larger ones with mounts. Choosing the right one depends on where you’ll display it and the look you're going for.
Standard A3 size in centimetres and inches
A3 paper measures 29.7 x 42 cm, which is roughly 11.7 x 16.5 inches. This is exactly double the size of A4. When you buy a frame labelled “A3”, it typically means the internal aperture is designed to fit this size of paper exactly. This style of frame will hold the sheet flush to the edge, offering a clean and straightforward finish.
It's important to check whether the A3 frame refers to the aperture or the external size, as this can vary between suppliers. The external frame size will always be larger than A3 due to the thickness of the frame moulding.
Framing A3 with or without a mount
There are two main ways to frame an A3 piece: using a frame that fits it exactly, or placing it within a larger frame that uses a mount (or mat) to create a border. A mount not only enhances the look but also protects the artwork from touching the glass, which is ideal for prints or photographs.
A common combination is to use a 40 x 50 cm frame with a mount cut to fit A3 in the centre. This adds a sense of scale and is often used for gallery-style displays. The mount opening will be slightly smaller than A3 to hold the paper in place — usually around 28.7 x 41 cm.
Choosing the right A3 frame
The best A3 frame depends on the type of piece you're displaying. Certificates and posters often suit simple clip frames or standard black or wood-effect frames that match the A3 size directly. For photography or fine art prints, using a mount inside a larger frame adds depth and visual focus.
If you’re planning to hang the frame, it’s worth checking that it includes the right fixings and whether it can be mounted portrait or landscape. Some cheaper A3 frames only support one direction.
Also consider the material — frames come in plastic, MDF, aluminium or solid wood. Each offers a different look and level of durability. For long-term display or higher-value pieces, opt for UV-protective glass or acrylic to guard against fading.
A3 frame sizes with mount options
Using a mount (also called a mat) gives your piece a more premium, gallery-style finish. Here are some common frame sizes that suit A3 with a mount:
- 40 x 50 cm frame with an A3 mount opening
- 50 x 70 cm frame for a bold visual impact with a wide mount
- 16 x 20 inch frame (a close alternative with a custom-cut mount)
These are popular choices for photographers and designers looking to elevate presentation without going for full custom framing.
Landscape vs portrait orientation
A3 is flexible and works in both orientations — portrait for certificates, menus, and posters, landscape for panoramic prints, wide photography and charts. Before buying, it’s important to check whether the frame supports both hanging directions. Some cheaper frames only offer fixings for portrait use, or require extra hardware for wall mounting in landscape.
Frame depth and protection
Standard A3 frames are designed for flat paper, but if you’re framing something textured — like a watercolour painting, collage, or signed memorabilia — you may need a deeper frame or a box frame. This gives room between the glass and the artwork, preventing pressure or smudging.
For valuable or archival work, look for frames with:
- UV-resistant glazing (to prevent sun fading)
- Acid-free mounts (to stop yellowing or damage over time)
- Non-reflective glass (for clear visibility in bright rooms)
Printing for A3 frames
If you’re printing artwork or photos specifically for an A3 frame, always make sure the final printed dimensions match the frame aperture exactly — 29.7 x 42 cm. If you're using a bleed (for full edge-to-edge printing), your design file should include an extra 3 mm on each side, making it 30.3 x 42.6 cm in total, which will be trimmed down during production.
Where A3 framing is commonly used
A3 is a favourite format for:
- Certificates and awards
- Art prints and photography
- Posters and event signage
- School projects and portfolios
- Menus, signage and display boards
It’s large enough to stand out, but small enough to remain practical in home, office or gallery settings.
Summary
An A3 frame is designed to fit 29.7 x 42 cm paper, or 11.7 x 16.5 inches. You can either use a frame that fits A3 exactly, or place it in a larger frame with a mount for a more refined display. Always check whether the size refers to the internal window or the outer dimensions, and choose the right materials and orientation for your setting.
