Matting
Double Mat Calculator
This double mat calculator sizes both windows of a double mat — the under-mat that grips the art and the larger top window you see — plus the reveal, the mat outside and the glass. It opens in Double mode: enter your artwork, overlap, reveal and border, and copy the exact cut sizes in inches or centimeters.
FramingMath · framingmath.com
Standard range ⅛–¼″ — enough lip to hold the art without hiding it.
Added to the bottom only. Typical ¼–1″.
Per side. Standard ¼″ (6 mm); typical ⅛–½″.
Optional — your photo stays on your device and is never uploaded. It’s cropped to fill the opening.
- Top opening (what you see)
- 8″ × 10″ approximately 20.3 × 25.4 cm
- Under-mat opening
- 7 1/2″ × 9 1/2″ approximately 19.1 × 24.1 cm
- Reveal (cut, per side)
- 1/4″ approximately 0.6 cm
- Mat outside
- 12″ × 14″ approximately 30.5 × 35.6 cm
- Borders (T / B / L / R)
- 2″ / 2″ / 2″ / 2″ approximately 5.1 cm / 5.1 cm / 5.1 cm / 5.1 cm
- Glass / backing cut
- 11 7/8″ × 13 7/8″ approximately 30.2 × 35.2 cm
Rounded to the nearest 1⁄16″ (1 mm). The converted second unit, and any per-side or divided figure, may differ by up to that much. Showing exact decimals (to 0.001″ / 0.01 cm). The converted second unit, and any per-side or divided figure, may still differ in the last place.
How the double mat calculator works
A double mat sets a second board behind the top one, so a thin band of the lower board — the reveal — frames the window with a slim accent line. This calculator opens in Double mode and returns the numbers you cut or order to: the top (visible) opening, the under-mat window that holds the art, the reveal per side, and the mat outside plus glass and backing.
Two windows, one rule. The under-mat is cut like any single mat, small enough to hold the print: under-mat window = artwork − 2 × overlap. The top mat’s window is cut larger by the reveal on every side, so you add it twice in each direction: top opening = under-mat window + 2 × reveal. The under-mat’s exposed edge is the reveal you see. The tool sizes both windows, then grows the outside and glass to match the top window — change any field and every number updates live, in inches with fractions or in centimeters.
Worked example: an 11 × 14 print with a ¼″ reveal
Take an 11 × 14″ print, a ¼″ overlap and a ¼″ reveal, with 2″ borders. The under-mat window is (11 − ½) × (14 − ½) = 10½ × 13½″. Add the ¼″ reveal on each side and the top window is 11 × 14″ — with a ¼″ overlap and a ¼″ reveal, the visible window lands right on the artwork size. Add the 2″ borders and the mat outside, the frame you order, is 15 × 18″; the glass and backing drop in about ⅛″ smaller, near 14⅞ × 17⅞″. Cut the under-mat and the top mat to the same outside — only the two windows differ.
How much reveal should show?
The reveal is pure accent, so its width is a design call. A ¼″ reveal — about 6 mm — is the classic, balanced choice and the tool’s default; it reads clearly without competing with the art. Drop to ⅛″ for a crisp pinstripe on small prints, or open up to ⅜–½″ for a bold band on large pieces. One limit is worth respecting: keep the reveal no wider than your overlap, or the top window opens past the edge the under-mat is gripping. For the cutting side — bevels, blade depth and matching an accent to the frame — the double matting & reveals guide goes deeper.
Choosing the accent (under-mat) colour
The reveal is the only place the under-mat shows, so its colour is the whole point of a double mat. The safe move is to pull a colour already in the artwork — a muted tone from the image reads as intentional rather than loud. Neutrals like cream, stone and black suit almost anything; a saturated accent — deep red, forest, navy — draws the eye inward and works when the art can carry it. Use the accent swatch under the preview to try colours against your art before you order; it changes the reveal in the preview only and never touches the sizes.
Common mistakes
- Cutting the top window smaller than the under-mat. The top mat has the larger window — top = under + 2 × reveal — not the other way round. Reverse them and the top mat hides the reveal completely.
- A reveal wider than the overlap. If the reveal exceeds the overlap, the top window clears the edge the under-mat holds and a sliver of the mount can show. Keep the reveal at or below the overlap.
- Reading the cut size as the face width. The figures here are the cut (opening) sizes. Because both windows are bevelled at 45°, a cut reveal shows a hair narrower on the face — a ³⁄₁₆″ cut reads as about ⅛″. Size to the openings above, not the bevel.
- Forgetting the frame depth. Two boards plus glass, art and backing stack thicker than a single mat; check the frame’s rabbet depth so everything seats.
Frequently asked questions
What is a mat reveal?
The reveal is the narrow band of the under-mat that shows around the window, framed by the top mat. It is the accent line a double mat is cut to produce, and this calculator reports it as the reveal per side.
What is the standard double-mat reveal size?
A quarter inch — about 6 mm — is the standard, and the calculator opens with it set. Most double mats sit between an eighth of an inch, a fine pinstripe, and half an inch, a bold band; a quarter inch reads as balanced on typical prints.
How do you calculate the top-mat opening?
Top opening equals the under-mat window plus twice the reveal. The under-mat window is the artwork minus twice the overlap, the same as a single mat; the top window is bigger by the reveal on all four sides, so you add it twice in each direction. The tool does both steps for you.
How much of the second mat should show?
As much as suits the piece. A quarter inch is the usual amount; drop to an eighth for a subtle line on small art, or open to three eighths or a half on large pieces. The reveal is even all the way around, so pick a width and the calculator holds it on every side.
Double mat vs single mat — which should I use?
Neither is better outright. A double mat adds depth and a line of accent colour, which lifts a plain print or ties the frame to the art; a single mat is simpler and cheaper. Reach for a double when you want that extra colour or a more finished, gallery look.
Does double matting make the frame thicker?
Slightly. The second board adds its own thickness to the stack of glass, mats, art and backing, so check the frame’s rabbet depth. If the moulding is shallow, a thinner backing or a deeper frame keeps everything seated.
What colour should the accent (under-mat) be?
Pull a colour from the artwork itself for a reveal that looks deliberate — a muted tone from the image is the reliable choice. Neutrals work with anything; a saturated accent draws the eye in when the art can carry it. Try options with the accent swatch before ordering.