A4 is one of the most common paper sizes used in the UK, especially for documents, certificates and prints. But when it comes to framing an A4 piece, many people aren’t sure what size frame to choose. Do you need an exact match or a slightly larger frame with a mount? Here’s everything you need to know to pick the right size frame for A4.
A4 paper size in centimetres and inches
A4 paper measures 21 x 29.7 centimetres, which is roughly 8.3 x 11.7 inches. These are the exact dimensions of the sheet, so if you want a frame that fits it perfectly edge to edge, the internal frame dimensions need to match those figures.
However, frames are often listed by the size of the image or item they’re intended to hold, not the outer size of the frame itself. So when shopping for an A4 frame, you’ll usually see “Fits A4” clearly indicated, which means the aperture (the window inside the frame) matches the A4 dimensions.
Frame styles for A4
You have two main options when it comes to framing A4 paper: a frame that fits A4 exactly, or a larger frame with a mount (also known as a mat).
An exact A4 frame is designed to hold the sheet without a border. It’s a clean, minimal option, especially good for certificates or notices. If you're after a more polished or gallery-style look, a frame with a mount can add impact. For instance, you might choose a 30 x 40 cm frame with a mount that has an A4-sized opening in the centre.
Mounts are especially useful if you're framing art or photography and want to draw attention to the piece while protecting the edges.
Choosing the right frame for your needs
The decision often comes down to where the frame will be displayed and what kind of look you’re going for. For home use, many people prefer a mount to make the piece feel more finished. In offices or educational settings, a straight A4 frame tends to be more functional and compact.
It’s also worth checking how the frame opens, whether it includes protective glass or acrylic, and how it will be hung or stood up. These small details can make a big difference depending on where the frame is going.
Outer frame dimensions vs. inner frame size
One thing that often causes confusion is the difference between the outer dimensions of a frame and the aperture (or inner size). The aperture is the space into which the A4 sheet fits — 21 x 29.7 cm. However, the external size of the frame will always be larger, as it includes the width of the moulding (the material around the edge) and any additional space taken up by a mount.
If you’re working with a tight wall space or gallery wall layout, it’s a good idea to check the full external measurements of the frame — especially if you’re mixing different frame sizes together.
Using a mount with an A4 frame
Mounts are often used to enhance presentation. A mount is a cardboard or foam board border placed between the image and the frame’s glass, offering both aesthetic appeal and physical protection. If you’re using a mount to frame an A4 piece, the mount opening should be slightly smaller than A4 to hold the paper securely — typically around 20 x 29 cm, leaving a small overlap to stop the sheet from falling through.
A common combination is a 30 x 40 cm frame with an A4 aperture in the mount. This setup gives the piece a more gallery-ready, high-end appearance.
Frame depth and material
Beyond height and width, frame depth can matter too, especially if you’re framing something with thickness — like textured artwork, raised prints or pieces with embellishments. Basic A4 frames are usually quite shallow and designed for single sheets of paper. If your piece is bulkier, consider a deeper box frame or shadow frame.
Materials also vary — from simple plastic or MDF frames to aluminium and solid wood. The material choice can influence not only the look but also the weight and durability, especially for wall mounting.
Portrait or landscape orientation
A4 can be used either portrait or landscape, so it’s important to check that the frame you choose supports both orientations — especially if it includes fixings for wall mounting. Many cheap frames only come with portrait hanging options, which can be limiting if you're framing a landscape photo or design.
Digital frames and non-standard uses
A4 frames are also used for more than just paper. People use them to display digital artwork, embroidery, certificates, posters and even jigsaw puzzles. In these cases, you might need acid-free backing, UV-protective glazing, or secure clips depending on the item’s value and fragility.
Summary
The standard A4 size is 21 x 29.7 cm, and frames that fit A4 are common and easy to find. You can choose a basic frame that fits A4 edge to edge, or opt for a larger frame with a mount to create a more polished look. Be sure to check whether the frame’s aperture fits A4 exactly, and consider whether you need features like dual orientation, deeper depth or higher-quality materials depending on what you’re framing.