About the Picture Frame Calculator
Framing a photo, print, or piece of art means stacking three layers inside a rectangle: the artwork itself, an optional mat border around it, and the frame moulding around that. This calculator uses the standard framing-industry approach to turn three simple measurements — artwork size, mat width, and frame (moulding) width — into the finished outer frame size, the size to cut glass and mat board, and how much moulding to buy.
The formulas
- Glass / mat cut size = artwork width + 2 x mat width, by artwork height + 2 x mat width. This is the size of the glass, backing board, and the outer edge of the mat board — it sits inside the frame's rabbet (the groove that holds everything in place).
- Finished outer frame size = glass/mat width + 2 x frame width, by glass/mat height + 2 x frame width. Equivalently, outer size = artwork size + 2 x mat width + 2 x frame width in each dimension.
- Moulding perimeter = 2 x (outer width + outer height). Because mitered 45-degree corners waste material and mistakes happen, this calculator adds a 10% allowance on top of the raw perimeter before converting to linear feet — a common rule of thumb used by framing suppliers.
- Moulding cost = moulding length (in feet) x number of frames x cost per linear foot.
Worked example
An 8 x 10 in photo with a 2 in mat border and 1.5 in frame moulding: the glass/mat size is (8+4) x (10+4) = 12 x 14 in, and the finished outer frame is (12+3) x (14+3) = 15 x 17 in. The moulding perimeter is 2 x (15+17) = 64 in; with 10% waste that is 70.4 in, or about 5.87 linear feet per frame.
How to get accurate results
- Measure the artwork itself, not the mat opening — mat width is entered separately.
- Set mat width to 0 if you are framing without a mat (frame moulding sits directly against the glass/backing).
- Frame moulding width is the visible face width of the moulding profile, measured from a sample or the supplier's spec sheet.
- Increase the number of frames to get a combined moulding length and cost for a matching set.
Frequently Asked Questions
How do I calculate the finished outer size of a picture frame?
Add twice the mat width and twice the frame (moulding) width to each dimension of the artwork: outer width = artwork width + 2 x mat width + 2 x frame width, and the same formula for height. An 8 x 10 in photo with a 2 in mat and 1.5 in moulding finishes at 15 x 17 in.
How much moulding do I need to buy?
Measure the perimeter of the finished outer frame size — 2 x (outer width + outer height) — then add roughly 10% extra for mitered 45-degree corner waste before converting inches to linear feet. This calculator applies that 10% allowance automatically and multiplies by the number of frames you enter.
What size should the glass and mat board be cut?
Glass, backing board, and the outer edge of the mat board should all match: artwork width + 2 x mat width, by artwork height + 2 x mat width. That rectangle fits inside the frame's rabbet, with the mat's inner window cut to the artwork's own size.