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Picture Frame Size Formula
The picture frame size calculator uses the picture size, mat border, frame face width, and frame overlap to estimate the mat opening, inside frame size, outside frame size, and glass or backing size.
- PW = picture width
- PH = picture height
- M = mat border size on each side
- F = visible frame face width
- O = frame overlap, meaning how much the frame lip covers the mat or picture
- MO_w, MO_h = mat opening width and height
- IF_w, IF_h = inside frame width and height
- OF_w, OF_h = outside frame width and height
- G_w, G_h = glass or backing width and height
The mat opening size matches the picture size entered. The inside frame size adds the mat border to all four sides. The outside frame size adds the frame face width to both sides, then subtracts the frame overlap from both sides. If the overlap would make the outside size smaller than the inside size, the result is limited to the inside frame size. The glass and backing size match the inside frame size.
Common Picture Frame and Mat Size References
These tables can help you check whether your result is close to a common frame or mat layout.
| Picture Size | Common Mat Border | Typical Inside Frame Size With Mat |
|---|---|---|
| 4 × 6 in | 1 in | 6 × 8 in |
| 5 × 7 in | 1.5 in | 8 × 10 in |
| 8 × 10 in | 2 in | 12 × 14 in |
| 11 × 14 in | 2 in | 15 × 18 in |
| 16 × 20 in | 2 to 3 in | 20 × 24 in or 22 × 26 in |
| Input | Typical Range | Notes |
|---|---|---|
| Mat border | 1 to 4 in | Small photos often use narrower mats. Larger art often uses wider mats. |
| Frame face width | 0.5 to 3 in | This is the visible width of the frame molding from the inside edge to the outside edge. |
| Frame overlap | 0.125 to 0.25 in | The calculator default is 0.25 in. Use the actual lip overlap if you know it. |
Example Picture Frame Size Calculations
Example 1: 8 × 10 picture with a 2 inch mat
Suppose your picture is 8 in wide and 10 in high. You use a 2 in mat border, a 1 in frame face width, and a 0.25 in frame overlap.
- Mat opening size: 8 × 10 in
- Inside frame width: 8 + 2(2) = 12 in
- Inside frame height: 10 + 2(2) = 14 in
- Outside frame width: 12 + 2(1) - 2(0.25) = 13.5 in
- Outside frame height: 14 + 2(1) - 2(0.25) = 15.5 in
- Glass or backing size: 12 × 14 in
Example 2: 5 × 7 picture with no mat
Suppose your picture is 5 in wide and 7 in high. You enter 0 for the mat border, 0.75 in for the frame face width, and 0.25 in for the frame overlap.
- Mat opening size: 5 × 7 in
- Inside frame width: 5 + 2(0) = 5 in
- Inside frame height: 7 + 2(0) = 7 in
- Outside frame width: 5 + 2(0.75) - 2(0.25) = 6 in
- Outside frame height: 7 + 2(0.75) - 2(0.25) = 8 in
- Glass or backing size: 5 × 7 in
FAQ
What size frame do I need for a picture with a mat?
Add the mat border to both sides of the picture width and both sides of the picture height. For example, an 8 × 10 picture with a 2 inch mat needs an inside frame size of 12 × 14 inches. The outside frame size then depends on the frame face width and overlap.
Is the glass size the same as the picture size?
Not usually. In this calculator, the glass and backing size match the inside frame size. If you use a mat, the glass covers the full matted area, not just the picture opening. If you do not use a mat, the glass size matches the picture size entered.
What should I enter for frame overlap?
Frame overlap is the amount of the frame lip that covers the edge of the mat or picture. If you do not know the exact value, 0.25 inches is a common estimate. For a more exact result, measure the rabbet lip or check the frame molding specifications.
