A 20 x 25 frame is measured across its inside opening, not its outer edge, so measure your artwork edge-to-edge and confirm whether the seller means inches or centimeters.
Buy the wrong size and you’re repacking a frame, paying return shipping, and starting over. The fix is ten minutes with a tape measure and one decision about what you’re actually measuring — the art, the mat opening, or the frame itself.
Here’s the part that trips people up before they even pick up a ruler: “20 x 25” doesn’t mean the same thing everywhere. In U.S. framing, it normally means a 20 x 25 inch frame. But in many standard size charts, 8 x 10 in equals 20 x 25 cm — a small photo size, not a wall-piece size. A listing that says “20 x 25” could be either. Check the unit before anything else.
Which Part of the Frame Do You Measure?
Frame size is measured from inside edge to inside edge — the opening, sometimes called the rebate. That’s the number sellers quote, and it’s the number your artwork has to match.
Wall-space planning is a different measurement. If you’re deciding where a frame hangs or how it looks above a sofa, use the outside dimensions, which include the frame molding and run larger than the opening.
Measure the wrong surface and you’ll order a frame that’s an inch or two off in every direction. Two tapes give you the honest picture: one for the opening, one for the outer trim.
How To Measure Your Artwork Step by Step
Measure the piece you want to frame edge-to-edge, flat on a level surface, with a ruler or tape accurate to 1/16 inch. If you use no mat, the art size should match the frame’s inside dimensions.
- Lay the artwork flat on a level surface.
- Measure width left-to-right, then height top-to-bottom.
- No mat? Measure the full artwork, including any borders.
- Using a mat? Measure only the area that will show through the mat window — not the full sheet or print.
- Reusing a frame? Pull the backing board and measure the board or the frame opening edge to edge. That’s your most accurate inside size.
- Thick piece? Check the frame’s rabbet depth so the artwork actually sits inside.
Write both numbers down in the order width x height. Width is always the horizontal number, height the vertical one — flipping them is one of the most common ordering mistakes.
If you’d rather skip the guesswork and start from frames that already fit standard art, browsing a tested selection of 20 x 25 frame options with real measurements saves a return trip.
American Frame’s measuring guide puts the core rule simply: use a ruler accurate to 1/16 inch, and frame size equals the picture size for standard formats when no mat is involved. American Frame’s artwork measuring guide walks through the opening, mat, and outside dimensions separately.
Where Sizing Goes Wrong
Most bad orders come from measuring the wrong surface, not from measuring badly. Confirm which dimension the seller means before you commit.
Frame It Easy’s guide notes that “frame size” sometimes means the opening and sometimes the outer edge, so buyers should confirm the convention. Adobe Express’s framing guide makes the same point: the frame’s inside dimensions are what the art must match.
| What You’re Measuring | Use It For |
|---|---|
| Frame opening (inside edge to inside edge) | Matching art or mat size when buying a frame |
| Mat window | Fitting the visible image area when a mat is used |
| Backing board | Reframing an existing piece with the most accurate inside size |
| Outside frame dimensions | Planning wall space and layout only |
The recurring mistakes: measuring the outside trim instead of the opening; including the mat in the artwork measurement; swapping width and height; and assuming every “20 x 25” listing uses the same unit system.
References & Sources
- American Frame. “Measuring Art” Frame opening, mat, and outside dimension guidance.
- Frame It Easy. “How to Measure a Picture Frame” Confirms frame size convention and measuring order.
- Adobe Express. “How to Measure a Photo Frame” Inside-dimension matching for photo framing.
