How to Size a Picture Frame | Measure the Opening, Not the Edges

To size a picture frame, measure the artwork’s visible image area or outer print size and match it to the frame’s inside opening, not its outside edges.

Most people pick up a tape measure and measure the outer edges of the frame they already own, then order the wrong size. The number a frame is sold as — 8×10, 11×14, 16×20 — refers to the space inside the frame where the art sits, called the rabbet. When sizing a picture frame, you match the artwork to that inside opening, and the whole process takes about two minutes with a ruler.

How To Measure Artwork For Framing

Lay the artwork flat on a table. Use a ruler or tape measure and record the width first, then the height, in that order. Write it down as Width × Height so you don’t mix them up later.

What exactly you measure depends on whether the print has borders you want to keep visible:

• Full outer print — measure edge to edge when you want the print’s white borders or margins showing inside the frame.
• Visible image only — measure just the image area if you plan to crop the borders behind a mat or if the print was made borderless.

If the art is unusually thick, or you plan to stack multiple mats, also measure the depth of the artwork and note it. A deep piece needs a frame with a deeper rabbet to fit without bowing the backing.

Matching Artwork To Standard Frame Sizes

Retail frames come in standard sizes, and your job is to find the one whose inside opening matches your measurement, or the next size up if you’re adding a mat. Common standard sizes include 4×6, 5×7, 8×10, 11×14, 16×20, 18×24, and 24×36, though availability varies by retailer. A classic pairing is an 8×10 image with an 11×14 frame and mat.

An internal lip on many frames overlaps the print’s edge by roughly 2–3 mm, so if your artwork is an exact fit, expect a tiny border to be covered. That’s normal, not a defect.

When To Use A Mat: Double The Measuring

Adding a mat changes the math. You now measure two things: the frame is sized to the mat’s outer dimensions, and the mat’s opening is cut to the artwork’s size. The frame never touches the art — it holds the mat, and the mat holds the print. If you’re buying a frame that comes with a mat, the stated frame size (say 11×14) refers to the mat’s outer size, not the visible image opening.

Common Framing Mistakes To Avoid

Three errors account for most wrong-size frame orders. The first is measuring the frame’s outer edges instead of the inside opening — the outside edge can be an inch or more larger than the actual viewing area. The second is mixing up width and height or switching unit systems mid-measurement. The third is ignoring the mat entirely and ordering a frame to the art size when you planned to add a mat, which shrinks the visible area and covers part of the image.

When a frame has glass or acrylic, and the art is delicate or thick, the rabbet depth and backing space matter. A proper fit leaves the art flat against the backing with the glass sitting clear of the surface. If the frame’s opening fits but the depth is shallow, the glass will press on the piece. When you need exact precision, measure to within 1/16 of an inch — which is also the standard most custom framers work to.

For very large prints, accurate measurements matter even more, since standard sizes jump quickly. If you’re framing a 50-inch print or larger, see our picks for the best 50 inch picture frame to see what’s available before you commit to a custom order.