How this instrument works
Framing shops size a matted frame with one simple rule: the frame opening in each direction equals the image dimension plus the mat border on both sides of it. A mat border only adds width once per side, but since it wraps all four edges, each dimension grows by twice the border width — once for the left/right pair, once for the top/bottom pair.
Mat width is a deliberate design choice, not just a spacer. Framing suppliers generally put an average border between about 1.5 and 3 inches, and many professional framers recommend something in the 2-to-4-inch range unless a specific tighter look is wanted — a wider mat gives artwork visual breathing room and makes a smaller piece read as more substantial on a wall.
The output is also a practical shopping tool. Photographers and gallery framers routinely add a mat specifically to make a smaller, non-standard print fit a common off-the-shelf frame size like 11×14 or 16×20, avoiding the cost of a custom-cut frame. Running the math the other way — choosing your image size and a mat width, then checking whether the result lands on a stock size — tells you before you buy whether a standard frame will work or whether you need one custom-made.
- Enter Image / photo width, inches — the outer edge-to-edge width of the actual print or artwork.
- Enter Image / photo height, inches — the outer edge-to-edge height of the print.
- Enter Mat border width, inches — the width of visible matting on all four sides; enter 0 for a frame with no mat at all.
- Read Frame opening width needed and Frame opening height needed — the size to buy or have a framer cut.
- If the result doesn't match a stock frame size, either nudge the mat width slightly or plan for a custom-cut frame at the exact dimensions shown.
Worked example — an 8×10 in photo with a 2 in mat
Enter 8 in for Image width, 10 in for Image height, and 2 in for Mat border width — a standard 8×10 photo with a generous, gallery-style border. Frame opening width needed comes to 8 + 2×2 = 12.0 in and Frame opening height needed comes to 10 + 2×2 = 14.0 in, so a 12×14 in frame is what to buy or order.
A narrower 1.5-inch mat around a smaller 5×7 in photo tells the same story on a common combination: 5 + 2×1.5 = 8.0 in wide by 7 + 2×1.5 = 10.0 in tall, exactly the popular 8×10 in stock frame size — a common trick for making a 5×7 print fit an off-the-shelf frame rather than paying for a custom one.
Questions
How wide should a mat border typically be?
Framing suppliers commonly cite an average border of about 1.5 to 3 inches, and many professional framers work within a 2-to-4-inch range unless a specific tighter or more dramatic look is wanted. Wider borders tend to make smaller artwork feel more substantial, while narrower borders keep more visual focus on the image itself — it's a style choice as much as a technical one.
Can I calculate the frame size for a print with no mat at all?
Yes — enter 0 for Mat border width, inches. With no mat, the formula simplifies to frame size equaling image size directly, since 2 × 0 adds nothing to either dimension. This matches a full-bleed print or a frame designed to hold the artwork edge-to-edge with no visible border.
My result isn't a standard frame size — what should I do?
Standard stock frames are typically sold in sizes like 5×7, 8×10, 11×14, 16×20 and similar increments. If your calculated size lands between two stock sizes, either adjust the mat border width slightly until it hits a stock size, as many framers deliberately do, or order a custom-cut frame at your exact calculated dimensions — more expensive, but exact.
Does the mat width have to be the same on all four sides?
This calculator assumes an equal border on every side, which is the standard convention and the easiest to price and cut. Some framers use a 'weighted' or 'bottom-heavy' mat with a slightly wider bottom border for visual balance — if you want that look, calculate the frame height using the larger of the top or bottom border width instead of a single uniform value.
Is the 'image size' the same as the paper the photo is printed on?
Not necessarily. This calculator treats Image / photo width and height as the portion you actually want visible inside the mat opening, not any white paper border printed around it — if your print has its own blank margin, measure only the photographic image area itself, since that's what the mat opening should be sized around.