Picture frame and mat calculator

How to use it

1. Enter the artwork width and height, and how far the mat covers it on each edge.
2. Enter the four borders. A weighted mat is usually a little deeper on the bottom.
3. Enter the moulding’s face width and the rabbet width. The reveal is the face that sits outside the glass.
4. Enter the kerf if you want a buying length for the stick. The length allows one kerf per piece.
5. Cut the long points to the outside size, or the short points to the glass size. Do not mix the two on one stick.

The formula

Opening = art − 2 × overlap. Outside = mat + 2 × (face − rabbet). Stick = 2 × (outside width + outside height) + 4 × kerf.

• Overlap. How much of the sheet the mat hides on each edge. The opening is what remains.
• Reveal. Face minus rabbet. It is the moulding you see beyond the glass.
• Long point. The outside measurement of that side. Short point is the glass measurement.

Worked example

An 8 by 10 inch sheet, covered ⅛ inch on every edge, opens to 7.75 by 9.75 inches. Borders of 2 inches, with 2½ inches on the bottom, make a mat 11.75 by 14.25 inches. The glass matches the mat.

Moulding with a 1 inch face and a ⅜ inch rabbet shows 0.625 inch of face outside the glass. The frame’s outside size is 13 by 15.5 inches. Those outside numbers are the long points of the 45° cuts. The glass sizes are the short points. Four kerfs of ⅛ inch bring the stick you should have on hand to 57.5 inches.

What it will not decide

• Rectangles with square corners only. A hexagon belongs on the miter page.
• It assumes the rabbet covers the edge of the glass and does not stick past the face.
• Standard 32 by 40 inch mat board is a warning in the result, not a second calculator. Odd mats are cut from a larger sheet.

Questions

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