For the full breakdown, see our best 20 x 24 Frame with Mat guide.
A sizing chart lists a 20 x 24 frame with a 15.5 x 19.5 mat opening for a 16 x 20 image, and that is the convention most custom framers cut to. The number that trips people up is not the frame — it is the mat opening, which is always smaller than both the frame and the print’s outer edges. Below is the opening math, the overlap that holds a print flat, and the one measurement worth taking before you order.
Mat Opening vs. Mat Outside Size
The mat opening is smaller than the mat itself, and the mat itself often matches the frame’s outer dimensions. A 16 x 20 mat fits a 16 x 20 frame; a 16 x 20 artwork rarely goes into a frame that small — it goes into something larger, usually 20 x 24, with a mat filling the gap.
That gap is the border you see between the frame and the picture. Notes from mat-cutting references put typical borders for this pairing anywhere from 2 to 4 inches per side, so 2.25 inches sits at the narrow end of normal.
- Frame size: the outside edge of the moulding — 20 x 24 here.
- Mat outside size: the full mat board, frequently cut to the frame size.
- Mat opening: the window the image shows through — 15.5 x 19.5 here.
- Overlap: the 1/4 inch or so of mat that rests on the print’s edge to hold it flat.
How Much Border Will You Actually See?
Border width is a taste call, not a rule, but it does change the look of the wall. A 2-inch border keeps the picture dominant; a 4-inch border turns the mat into part of the composition and suits larger rooms. Anything tighter than about 1.5 inches starts to feel cramped next to a wide frame, and anything past 4 inches for a 16 x 20 print tends to swallow it.
Here is how the common 16 x 20 pairings compare:
| Frame Size | Typical Mat Opening | Best For |
|---|---|---|
| 16 x 20 | 15.5 x 19.5 or no mat | A snug, gallery-style look with a thin frame |
| 20 x 24 | 15.5 x 19.5 | The standard pairing, about 2.25 inches of border |
| 24 x 30 | 15.5 x 19.5 | A wide statement border of roughly 4 inches and up |
| 20 x 24 (float mount) | None — print sits on top | Showing the full sheet, including white margins |
Does Every 20 x 24 Frame Fit a 16 x 20 Print?
No.
Frame construction varies, and so does the exact mat cut. Published guides note small overlaps of 1/8 inch or 1/4 inch per side depending on the cutting standard used, and that difference decides whether a print sits flat or buckles. Whether the image should be snug, float-mounted, or shown with a visible border changes the cut too, so two frames labeled 20 x 24 can take different mats.
Measure before you buy. Take the print’s true dimensions, then check the frame’s rabbet depth and the mat’s listed opening — not the mat’s outside size. When you are ready to compare options, this roundup of the best 20 x 24 frame with mat covers models that list their actual opening dimensions.
What Goes Wrong With Mat Sizing
Most sizing mistakes come from reading the wrong number off the spec sheet, and both of the common ones are easy to avoid.
- Confusing mat outside size with the opening. A “16 x 20 mat” may describe the board’s outer edge, not the window. Ask for the opening.
- Assuming the frame size is the print size. A 20 x 24 frame does not mean a 20 x 24 picture; it usually means a 16 x 20 picture plus mat.
- Skipping the overlap. Without that 1/8 to 1/4 inch of mat over the print edge, the image can shift or bow behind the glass.
Get the opening right and the rest of the job is simple: the print centers itself, the border stays even all the way around, and nothing needs re-cutting.
FAQs
Can I put a 16 x 20 print in a 20 x 24 frame without a mat?
Yes, but the print will float inside the frame with visible gaps on all sides, since the frame is four inches wider and four inches taller. A mat fills that gap and holds the print flat. Without one, you would need to mount the print to a backing board sized to the frame.
Is a 2-inch mat border too narrow for a 16 x 20 picture?
No. A 2-inch border is a normal, slightly tight look that keeps the image dominant, and the standard 20 x 24 pairing lands near that at about 2.25 inches per side. Borders of 2 to 4 inches per side are the typical range for this print size.
What is the difference between mat size and mat opening?
Mat size describes the full board, which often matches the frame’s outer dimensions. The opening is the smaller window the picture shows through. For a 16 x 20 image in a 20 x 24 frame, the board is roughly 20 x 24 while the opening is about 15.5 x 19.5.
References & Sources
- Frame Destination. “Guide to Frame and Mat Dimensions for Common Print Sizes” Publishes the 20 x 24 frame with 15.5 x 19.5 mat opening for a 16 x 20 image.
- Frame Destination. “Mat Openings” Explains how mat openings are cut and how overlap holds a print in place.
- Shotkit. “Frame Mat Dimensions for Prints” Lists typical mat borders and frame pairings for common print sizes.
