What Size Mat for a 16×20 Frame? | The Correct Fit

For a 16×20 frame, use a mat with a 15.5×19.5 opening if the artwork is 16×20, sized to overlap the print’s edges slightly.

For the full breakdown, see our best 15 x 20 Frame guide.

When you’re framing a 16×20 print, the mat size you need depends on whether you want a border. If the artwork itself is 16×20 and you want a mat around it, a 20×24 frame with a mat opening of 15.5×19.5 is the standard, reliable setup. This lets the mat overlap the print by about a quarter inch on each side, holding it securely in place. If you skip the mat entirely, a 16×20 frame holds a 16×20 piece directly.

How Mat Sizing Works for 16×20 Artwork

Mat openings are typically cut about 1/4 inch smaller than the artwork on each side. That overlap is what keeps the print from sliding around inside the frame. The math is simple: subtract half an inch from both the width and height of your artwork to get the opening size. For a 16×20 print, that works out to a 15.5×19.5 opening.

The critical distinction to understand is that the mat’s outside dimensions and its opening size are two completely different numbers. The outside dimension determines which frame you need. The opening size determines how much of the artwork shows. Mixing these up is the most common framing mistake.

Mat Size Options for a 16×20 Frame

Here is what actually fits, depending on what you’re framing:

• No mat, artwork is 16×20: A 16×20 frame holds the print directly with no border.
• Matted 16×20 artwork with a border: A 20×24 frame is the standard choice, paired with a mat whose outside size is 20×24 and whose opening is 15.5×19.5.
• Smaller artwork, like 11×14, inside a 16×20 frame: A mat with a 16×20 outside size and a 10.5×13.5 opening correctly centers and frames an 11×14 print.

This sizing pattern is widely used across framing suppliers. Frame Destination’s guide to print sizes lists these as the standard pairings for common artwork dimensions, and MatBoard Plus explains the opening-size math in its sizing guide.

Choosing the Right Frame for Your Mat

Before you buy, measure your artwork’s exact outer edge. Then decide whether you want a mat border. If you do, pick a frame that matches the mat’s outside dimensions, not the artwork size. A matted 16×20 print needs a 20×24 frame because the frame’s glass and backing are sized to the mat, not the art.

Frame size and mat opening are not interchangeable terms. A 16×20 frame is sized for an unmatted 16×20 piece or a mat whose outside size is 16×20. Buyers who skip this check often end up with a frame too small for their matted piece, and they have to start over.

Mat compatibility also depends on the frame’s inner rabbet fit and glass size, which sellers describe differently. Some list only the opening size; others list only the outside mat size. If you have your framing ready, a roundup of vetted frame options for 15 x 20 artwork can help you match the right product to your mat.

Mat Board Quality and Fit Considerations

When you’re comparing mats, check the product’s listed outside size against the frame’s inner dimensions, not just the opening. Two mats can share the same outer size but have different openings for different artwork sizes. Always confirm both numbers so the mat actually covers the edges of your print.

For preservation, look for mats described as acid-free with a white core. Acid-free matboard prevents the acids in ordinary cardboard from leeching into your artwork over time, which causes yellowing and discoloration. This matters most for prints you plan to keep for years.

The safest sequence when shopping is: measure the artwork first, decide on the border, then match the frame to the mat’s outside size and confirm the opening is about a quarter inch smaller than the art on every side. That order prevents nearly every common framing mistake.

The general rule holds across all sizes: the opening runs about 1/4 inch smaller than the artwork per side. For an 8×10 print, that gives a 7.5×9.5 opening. For an 11×14, it gives the 10.5×13.5 opening listed above. When you check a product listing, the outside size tells you which frame you need, and the opening size tells you which artwork fits.