Standard mat sizes

How pre-cut mat sizes work

A pre-cut mat is labeled by two sizes: its outer size, which matches a stock frame, and the print it fits. So “11×14 for 8×10” means an 11×14 mat (also called a mount, in the UK) with a window cut for an 8×10 photo.

The window — the opening or aperture — is cut a little smaller than the print so the mat overlaps the edges and holds it in place. The standard overlap is ¼ inch on each side, which takes ½ inch off each dimension: an 8×10 print becomes a 7½ × 9½ inch opening.

Whatever’s left between the opening and the frame is the border. Because most prints aren’t the same shape as the frame, the side and top/bottom borders usually differ — that’s the two numbers in the “Border” column. New to matting? Start with how to measure your art, then how wide to make the border.

Worked example: an 8×10 in an 11×14 mat

Start with the 8×10 print and the 11×14 mat. Cut ¼ inch off each side for the overlap and the opening is 7½ × 9½ inches. Subtract that from the 11×14 outer size and halve it: the borders come out to 1¾ inches at the sides and 2¼ inches top and bottom.

Prefer the picture to sit a touch high — the gallery look? Add a little to the bottom border (“bottom-weighting”). Work out any opening in the mat opening calculator, or design the whole mat in the mat border calculator.

Common mistakes

• Ordering by frame size alone. A mat needs both numbers — the outer size and the print it fits. “16×20” isn’t enough; “16×20 for 11×14” is.
• Expecting the opening to equal the print. The window is cut smaller on purpose so the mat can overlap and grip the edges. A 7½ × 9½ opening is correct for an 8×10 photo.
• Ignoring the overlap amount. Most mats use a ¼-inch overlap; some use ⅛ inch. If your print is borderless, too little overlap can let a white edge show.

Cutting your own from a blank

If you cut your own, mat board comes as pre-sized blanks (8×10 up to 24×36) and as a 32×40 inch full sheet — the common North-American full-sheet size, from brands like Crescent and Bainbridge; some suppliers also stock an oversize 40×60. A blank in your frame’s size saves trimming the outside, so you only cut the opening.

Cutting several openings in one board? Lay them out in the multi-opening mat calculator.

Board basics: ply and conservation

Two specs decide how a mat board behaves. Ply is its thickness: standard 4-ply is about 1⁄16 inch — right for almost everything — while 8-ply is close to twice that, so the bevel cut around the window shows a chunkier, more substantial edge — just make sure your mat cutter can be set deep enough to cut the thicker board cleanly.

The second spec is what the board is made of. Plain paper-faced board has an acidic wood-pulp core that can yellow artwork and raise brown foxing spots over the years; acid-free board resists that, and conservation or cotton-rag board (lignin-free, the museum choice) is best for anything you’d hate to lose. Note that acid-free and buffered aren’t the same thing — buffered board adds an alkaline reserve that suits most art but is best avoided against photographs, which prefer unbuffered, PAT-passed (Photographic Activity Test) materials. The matting glossary defines ply, foxing and conservation board in full.

A quick rule of thumb: for everyday photos, 4-ply acid-free board is plenty; save 8-ply and cotton-rag for original art, fine-art prints, and anything signed or irreplaceable. And note the mat lip only rests on the art — for those valuable pieces, hold the work with reversible hinges, archival photo corners or edge strips rather than the mat opening alone, which is not a conservation mount.