Can you reuse a frame you already own?

Do not use the decorative outside size.

The moulding around a frame contributes to its outside width and height. Those measurements cannot be substituted for the size of the board inside it. Identify the actual component space and the manufacturer’s fitting instructions, or measure a sound existing mat or backing that fits correctly as a reference.

Record width and height in the display orientation. A listing’s nominal frame size is useful for identification, but it is not a measurement of your particular assembly. Do not force components into a tight or out-of-square frame.

Test the actual paper footprint.

A window can be smaller than a board even when the paper would extend beyond the board edge. Our planner checks the paper’s placement behind the opening as well as the opening itself. Each board border must be at least as large as that edge’s chosen paper coverage for this flat rectangular layout.

For example, an 8 × 10 sheet with 1/8-inch coverage fits geometrically behind a centered window in an 11 × 14 board. Its window is 7 3/4 × 9 3/4; left/right borders are 1 5/8 and top/bottom borders 2 1/8 inches. The sheet starts 1 1/2 inches from the board’s left edge and 2 inches from its top edge. This proves a two-dimensional placement, not a manufactured fit.

Compare candidates without inventing stock.

Enter candidate board sizes into the comparison tool, one width × height per line. The initial numbers are examples, not a list of available frames. Set your own minimum border preference. A row can fit the paper yet fall short of that visual preference; these are different results.

The optional rotated comparison swaps candidate width and height. It does not establish that the hanging hardware, artwork orientation or existing frame can be rotated. Check those separately. A candidate that passes geometry may still be unavailable or unsuitable.

Depth and clearance remain open.

Glazing, mat layers, paper and backing form a stack. The frame must accommodate that stack and its securing method. A two-dimensional board calculation cannot establish rabbet depth, allowable clearance, board thickness or conservation suitability.

There is no universal fitting allowance built into this tool. Use the frame maker’s requirements or a framer’s measurement of the actual assembly. Treat a warped frame, fragile glazing, loose joints or a valuable original as a reason to seek appropriate help rather than a reason to force the fit.

Before buying a replacement mat.

Confirm the board’s exact outside size and practical clearance with the supplier. Check the exact window, display orientation, protected edge details and materials. Keep the old mat until the replacement has been checked; a nominal match is weaker evidence than the verified actual measurements.