Frame Size Calculator

Determine the correct frame size for your artwork with mat borders and moulding.

Frame Preview

Artwork400 × 300 mmMat570 mm outer470 mm outer
Required Frame Inner Size
530 × 430 mm
Glass/backing size needed (artwork + mat borders)
Mat Opening
394 × 294 mm
Visible artwork area (3mm overlap each side)
Overall Outer Size
570 × 470 mm
Total frame footprint on the wall
Mat Visible Area
65 mm each side
Visible mat border around artwork
Artwork Size
400 × 300 mm
Your artwork dimensions as entered

Closest Standard Frame Sizes

No standard frame sizes are close to your required dimensions. Consider custom framing.
Frame inner size = artwork + mat borders. When buying a frame, the listed size usually refers to the inner (glass) dimensions. Make sure to check whether a frame listing refers to inner or outer size before purchasing.

How to Use This Calculator

  1. 1

    Measure your artwork

    Measure the visible area of your art piece. This is the width and height of the image or print that you want to display within the frame.

  2. 2

    Set mat borders

    Choose uniform mat borders for equal spacing on all sides, or switch to custom mode to set different widths for top, bottom, left, and right. A slightly larger bottom border is traditional for visual balance.

  3. 3

    Add frame moulding

    Enter the width of your frame moulding profile. This is the visible border of the frame itself around the mat. Typical moulding widths are 15-40mm.

  4. 4

    Read frame size

    The calculator shows the required frame inner dimensions (glass/backing size). This is the size you need when shopping for a frame. The overall outer size includes the moulding width.

  5. 5

    Check standard sizes

    See which off-the-shelf standard frame sizes are closest to your requirements. If a close match exists, you may be able to adjust the mat borders slightly to fit a standard frame and save on custom framing costs.

Frequently Asked Questions

What is mat overlap?

Mats typically overlap the artwork by 3-6mm on each side to hold it in place. This means the visible opening of the mat is slightly smaller than the full artwork dimensions. The overlap ensures the art stays securely behind the mat without slipping. This calculator accounts for a standard 3mm overlap on each side when showing the mat opening size.

How do I choose mat border width?

Standard mat border width is 50-75mm (2-3 inches). The bottom border is often made 10-15mm larger than the top for visual balance, as equal borders can make the bottom appear narrower due to an optical illusion. Larger artworks generally benefit from wider mat borders, while very small pieces may look best with proportionally generous borders.

What if no standard frame size fits my artwork?

If no standard frame size matches, you have a few options. Consider custom framing for a perfect fit. Alternatively, adjust your mat border widths to accommodate the nearest standard frame size. You can also look for oversized standard frames and use wider mat borders to fill the extra space, which can actually enhance the presentation.