Picture Frame Mat Calculator
Frame width (in)
12.00
Frame height (in)
14.00
How it works
A mat creates the space between artwork and glass, preventing the artwork from touching the glass and providing a visual border. The Picture Frame Mat Calculator computes the outer mat dimensions and window opening size from the artwork dimensions and desired border widths.
**Standard mat formulas** Outer mat size = frame rabbet size (frame's inner edge). Window opening = artwork dimension minus the overlap (typically 1/8 to 3/16 inch on each side). A 5x7 inch photo with a 2-inch mat border: outer mat = 9x11 inches, window opening = 4.75x6.75 inches.
**Weighted bottoms** Traditional framing uses a slightly larger bottom mat border to compensate for an optical illusion that makes equal borders look bottom-heavy. A common rule: add 25 to 50% to the bottom border. For a 2-inch top and side border, use 2.5 inches on the bottom.
**Double matting** Double mats use two mat layers — an outer mat and a smaller inner mat of contrasting color. The inner mat typically shows 3/16 to 1/4 inch below the outer mat window. Add the reveal width to the inner mat window dimensions to calculate the outer mat window.
**Mat cutting** Professional mat cutters use a 45-degree bevel cut for clean edges. Test cuts on scrap mat board before cutting finished material.
Privacy: all calculations run in the browser. No data is transmitted.
Frequently Asked Questions
- Standard mat board is approximately 1/16 inch (1.5mm) thick — called 4-ply. This is the most common thickness for single mats. 8-ply mat board is twice as thick and provides a more substantial shadow between artwork and glass; preferred for valuable artwork and museum-quality framing. The thickness affects how much depth separation exists between the artwork and the glass — important for pastel and charcoal drawings where the medium would smear if touching glass. For charcoal, pastel, or media that might stick to glass, always use at least 4-ply mat, or use a double mat for extra depth clearance.
- Conservation mat board (also called acid-free or archival mat board) is made from alpha-cellulose or cotton rag materials and has a neutral or slightly alkaline pH. Standard mat board is made from wood pulp and is acidic — over time, the acid migrates to artwork and causes yellowing, fading, and deterioration. For original artwork, photographs, and items with sentimental or monetary value: always use conservation/acid-free mat board and backing board. For posters and prints you don't mind degrading: standard mat board is acceptable and cheaper. Conservation mat board costs 2–4x more than standard but protects artwork indefinitely.
- For double matting, you have an outer mat and an inner mat (called the reveal). The outer mat shows its full border width; the inner mat peeks out below the outer mat window — this reveal is typically 1/4 inch on all sides. Calculation: outer mat window = inner mat window + 2 × reveal width (e.g., if inner mat window is 5×7 and reveal is 1/4 inch: outer mat window = 5.5×7.5 inches). Outer mat size = same as frame rabbet. Both mats use the same outer dimensions; only the window openings differ. Use contrasting colors where the reveal shows — typically a darker inner mat with a lighter outer mat, or a complementary color combination.
- Yes, but with compromises. A utility knife and metal straight-edge can cut mat board — but produces a 90-degree (perpendicular) cut, not the 45-degree bevel that professional mat cutters create. The bevel cut (angled inward away from the window) is aesthetically superior because it creates a white or colored reveal along the window edge. For a clean utility knife cut: score deeply on the first pass, then cut through on the second pass. Use a very sharp blade — dull blades tear rather than cut. For oval and curved windows, you need specialized tools or a professional service. A handheld mat cutter (Logan Compact or similar, around $30–50) creates proper bevel cuts and is worth buying if you frame more than a few pieces.