Picture Frame Calculator - Mat, Frame, and Molding Length
Use this picture frame calculator to read outer, inner, and mat dimensions, the glaze size, and the total molding length from your picture size, mat, border, and rabbet width.
Picture Frame Calculator
Results
What Is the Picture Frame Calculator?
A picture frame calculator turns the size of a photo, print, or artwork into the outer and inner frame dimensions, the mat board and glaze size, and the total molding length for a custom frame.
- • Frame a standard photo print: Pick the right ready made frame for a 4x6, 5x7, 8x10, 11x14, or 16x20 print, with or without a mat.
- • Plan a mat for a print: Read the mat board and inner frame opening from your picture and frame dimensions.
- • Buy molding for a custom frame: Calculate the linear length of molding for a four corner mitered frame.
- • Solve the inverse mat problem: If you already own a frame, read the mat size that fits your picture.
Picture frames are described by four numbers: picture size, mat size, border or molding width, and rabbet depth. The first three set how big the frame is. The fourth sets how deep the recess is for the mat, glazing, and back panel.
Window measurements follow a similar pattern, so the curtain size calculator returns width, length, and total fabric for a curtain from your window size, fullness ratio, and rod height.
How the Picture Frame Calculator Works
The picture frame calculator runs three nested formulas. The outer dimensions add the picture, twice the mat, and twice the border. The inner dimensions subtract the rabbet from the mat. The total molding length is the perimeter of the outer frame for four mitered corners, with every input in the same unit (in or cm).
- Picture height and width: The vertical and horizontal size of the photo, print, or artwork.
- Mat height and width: The top/bottom and left/right mat border between the picture and the frame.
- Border (molding) width: The width of the picture frame molding, the wood or metal strip that forms the frame edge.
- Rabbet width: The depth of the recess where the mat, glazing, and back panel sit. About 0.25 in.
- Fudge factor: A small clearance added to the mat board size so the glazing drops in without binding. About 0.05 in is standard.
The mat board size is the picture plus twice the mat on each side. The glaze size is the mat board plus the fudge factor, so the glazing drops into the rabbet without binding. The total molding length is the perimeter of the outer frame for four 45 degree mitered corners.
Frame a 4x6 photo with a 1 inch border and no mat
Picture 4 in x 6 in, mat 0, border 1, rabbet 0.25, fudge 0.05.
outer = 4 + 2 * (0 + 1) = 6 in. outer width = 6 + 2 * (0 + 1) = 8 in. inner = 4 + 2 * (0 - 0.25) = 3.5 in. inner width = 6 + 2 * (0 - 0.25) = 5.5 in. perimeter = 2 * (6 + 8) = 28 in.
Outer 6 x 8 in, inner 3.5 x 5.5 in, glaze 4.05 x 6.05 in, total molding 28 in.
A 4x6 photo with a 1 inch border and no mat is a small table or shelf frame, and an 8x10 print with a 2 inch mat and 1 inch border follows the same pattern and gives 14x16 outer, 11.5x13.5 inner, 60 inches of molding.
Read the mat the other way: mat = (inner frame - picture) / 2 + rabbet. An 11.5x13.5 inner frame around an 8x10 print with a 0.25 rabbet gives a 1.75 inch mat, close to a standard 2 inch mat. The same rule reverses the build for any frame you already own.
According to NIST Special Publication 811, the inch is defined as exactly 25.4 millimetres, so a 1 inch border, mat, or rabbet is also 2.54 cm and the same formula works in either unit as long as every input uses the same unit.
Once you know the outer frame size, the wall square footage calculator reads the wall area so you can plan the gallery wall layout and the spacing between the frames.
Key Concepts Explained
Four ideas explain almost every result: how the border, mat, and rabbet stack to make the outer frame, how the inner frame opening relates to the mat and rabbet, how mitered corners set the molding length, and why standard print sizes exist.
What the border (molding) is
The border is the wood or metal strip that forms the visible edge of the frame. The border width sets how thick the frame looks.
What the mat does
The mat is the card between the picture and the glazing. Mat height is the top and bottom border, mat width is the left and right border, and the mat window is the cutout that shows the picture.
What the rabbet is
The rabbet is the L shaped recess cut into the inside back of the molding. The mat, glazing, and back panel drop into the rabbet. The rabbet width is the depth of that recess, typically 0.25 in or 6 mm.
Why standard print sizes matter
4x6, 5x7, 8x10, 11x14, and 16x20 are the photo print sizes most stores and ready made frames use. A standard size means a ready made frame and a 2 inch mat work out balanced.
A useful mental model is to stack the pieces from the picture outward: the picture sits in the center, the mat borders sit on each side, the molding adds the border width, and the rabbet removes a small depth so the mat and glazing sit inside the frame.
Picture frame molding and baseboard trim share the same perimeter math, so the baseboard calculator reads the room dimensions, subtracts the door and window openings, adds a waste factor for mitered corners, and returns the total linear feet of trim you need to buy.
How to Use This Calculator
Pick the unit on your ruler, enter the picture, mat, border, and rabbet, and the page returns the outer and inner frame dimensions, the mat board and glaze size, and the total molding length in real time.
- 1 Choose the unit: Pick inches or centimeters from the unit menu. The page does the math in the unit you enter.
- 2 Enter the picture size: Type the picture height and width. Standard photo prints are 4x6, 5x7, 8x10, 11x14, and 16x20.
- 3 Set the mat size: Enter the mat height (top/bottom) and mat width (left/right). Use 0 for no mat, or 1.5 to 3 inches for a gallery mat.
- 4 Set the border and rabbet: Type the border or molding width, then the rabbet width. A standard frame uses a 1 inch border and a 0.25 inch rabbet.
- 5 Add a fudge factor: The default fudge factor is 0.05 inches. Lower for tight fits, raise for thicker glazing.
- 6 Read the results: The page shows the mat board and glaze size, the outer and inner frame dimensions, and the total molding length.
An 8x10 print with a 2 inch mat and 1 inch border fits a 14x16 outer frame with an 11.5x13.5 inner opening and needs 60 inches of molding for four mitered corners.
Frame size and TV size are part of the same room layout, so the TV viewing distance calculator reads the TV size and viewing angle and returns the recommended seating distance and eye height for a comfortable layout.
Benefits of Using This Calculator
A short check before you cut, buy, or hang a frame saves molding, mat board, and the cost of a custom frame shop. The picture frame calculator returns the parts list in one pass.
- • Pick the right ready made frame: Match the outer size to a 4x6, 5x7, 8x10, 11x14, or 16x20 print.
- • Save molding and mat board: Calculate the linear molding length so you buy the right stick and the right mat board sheet.
- • Plan a gallery wall: Read the outer height and width for every frame so you can space and balance the wall before you drill.
- • Solve the inverse mat problem: If you already own a frame, read the mat size that fits inside it so you can pick a matching print.
Treat the result as a working number, not a final answer. The mat color, glazing thickness, frame finish, and back panel can all shift the exact cut, so leave a small fudge factor and dry fit first.
The same idea reverses when you already own a frame. The inverse mat formula lives a few paragraphs up under How the Calculator Works.
Factors That Affect Your Results
Custom frames are not a perfect stack of rectangles. These four factors explain why two frames built to the same numbers can still need a small tweak at the bench.
Miter saw accuracy
A 45 degree miter can drift a degree or two on a hand cut, adding a small gap or overlap at the corners and a small extra allowance to the molding length.
Mat board thickness and glazing
Mat board, glazing, foam board, and the back panel all add to the stack that fits in the rabbet. A thicker glazing or a double mat may push the stack past the rabbet depth.
Fudge factor and tolerance
A 0.05 inch fudge factor is the standard allowance. A larger one is fine for thick glazing, but a tight one on a hand cut mat can cause binding in the rabbet.
Rounding to two decimals
The page rounds every result to two decimals, which is fine for everyday framing but may shift the centimetre value by 1 mm on a 30 cm frame.
- • The page assumes a rectangular frame with four 45 degree mitered corners. Round, oval, or shadow box frames need different geometry and molding length.
- • The fudge factor is added to the mat board size only, not to the outer frame dimensions, so the page cannot simulate a bottom weighted mat.
If you need a museum grade frame for an exhibition, treat the page as a planning tool. The frame shop can adjust the mat, glazing, and molding profile to fit a high value print or a conservation grade mat.
According to NPS Conserve O Gram 13/1, the window cut into a mat must allow full viewing of the image and cover the object's edges for handling protection, and museum quality matboard is 100 percent cotton fiber buffered with calcium carbonate.
For the accent wall behind the gallery, the paint calculator reads the wall dimensions and the paint coverage rate, and returns the gallons of primer and paint needed to repaint the wall.
Frequently Asked Questions
Q: How do I calculate the size of a picture frame?
A: Add the picture height to twice the sum of the mat height and the border width to get the outer frame height. Do the same with the picture width, the mat width, and the border width for the outer frame width. An 8x10 print with a 2 inch mat and a 1 inch border has a 14x16 inch outer frame.
Q: What is the standard mat width for a picture frame?
A: The standard mat border for an 8x10 print is 2 inches on the top, bottom, left, and right. Smaller prints often use a 1.5 inch mat, and large gallery prints can use a 3 inch mat or a double mat with a 2 inch outer border and a 0.25 inch inner border.
Q: How much molding do I need for a custom picture frame?
A: The total molding length is the perimeter of the outer frame, twice the sum of the outer height and width. For a 14x16 frame you need 60 inches of molding for four 45 degree mitered corners, plus a small extra allowance for the joint waste.
Q: What is rabbet width in a picture frame?
A: The rabbet is the L shaped recess cut into the inside back of the molding. The rabbet width is how deep that recess is, usually 0.25 inches or about 6 mm. The rabbet holds the mat, the glazing, the picture, and the back panel.
Q: How do I calculate mat size from picture and frame dimensions?
A: Subtract the picture size from the inner frame size, divide by 2, and add the rabbet width. For a 14x18 inch frame around an 8x11 print with a 0.25 inch rabbet, the mat height is (14-8)/2 + 0.25 = 3.25 inches and the mat width is (18-11)/2 + 0.25 = 3.75 inches.
Q: What size frame do I need for an 8x10 picture?
A: An 8x10 print fits a 10x12 frame with a 1 inch border and no mat, or a 14x16 frame with a 2 inch mat and a 1 inch border. A 16x20 frame with a 3 inch mat and a 1 inch border is the gallery wall size, and an 18x22 frame with a 4 inch mat and a 1 inch border is the museum size.