What Does Matted Mean Picture Frame? | The Mat Board Explained

A matted picture frame includes a flat, paper-based mat board between the artwork and the glass, creating visual space and keeping the image from touching the glazing.

When you’re shopping for frames, the word comes up constantly, and so does its opposite. A matted picture frame contains that border; an unmatted one skips it, letting the image sit right against the glass. The distinction matters for looks, for protection, and for how the piece reads on a wall.

What A Mat Actually Does Inside A Frame

The mat is a thin, flat, paper-based layer placed between your photo or art and the glazing. It serves two jobs at once: it decorates the piece with a clean border, and it acts as a protective spacer that keeps the image from touching the glass. Without that gap, moisture can trap against the print and cause sticking over time.

Every mat has two separate measurements, and confusing them is the most common framing mistake:

• Opening size — the cutout window that shows the image.
• Outer or frame size — the outside dimension that fits inside the frame.

Ordering a mat means getting both numbers right, and they are not interchangeable.

How Do You Size A Mat Correctly?

Measure the visible artwork itself, not the full paper backing, then decide how wide you want the border. Framing guidance suggests the opening should overlap the artwork slightly — at least 1/8 inch on all sides — to keep the edges covered. Other guides recommend openings about 1/4 to 1/2 inch smaller than the art, with typical borders of 2 to 4 inches for most pieces.

The math is straightforward:

1. Measure the artwork’s width and height.
2. Pick a border width (2 to 4 inches works well for most pieces).
3. Add twice the border width to each dimension to get the outside mat size.
4. Check that the outside size matches your frame’s usable inside space.

Larger artworks often look better with wider borders, keeping the mat in proportion to the piece. If you’re using a standard-size frame, sticking to a standard mat size saves money and avoids custom cutting.

The frame’s internal depth matters too. Between the mat, the glazing, and the backing, everything must fit within the frame’s rabbet depth without pressing on the art.

Matted vs Unmatted: How To Choose

Mats add a gallery-style, finished look and give the eye a resting place around the image. They’re also a real safeguard: the spacer effect stops the print from touching the glass. Unmatted frames keep things simple and modern, but you lose that protective gap.

For archival or valuable prints, look for preservation-quality mats and museum-grade boards. Framing suppliers carry these options, though quality varies by manufacturer.

If you’re working with a standard size and want a ready-made option, a roundup of popular 8.5 x 11 matted picture frames can save you a trip to the custom cutter.

Common Matting Mistakes To Skip

Most framing errors trace back to a few mix-ups. Cut the opening too large and the artwork edges show through or fall into the window. Measure the paper edge instead of the visible image and your mat hides part of the print. Pick a border too narrow for the frame and the frame overpowers the piece.

The other fix is physical: don’t cut the mat so tight it presses on the artwork. A snug, comfortable fit keeps everything flat without distortion. When you’re unsure, a slightly larger border costs less than a recut.