Example Data Table
| Artwork |
Mat Borders |
Overlap |
Frame Face |
Estimated Outside Size |
| 8 x 10 in |
2, 2, 2, 2.5 in |
0.125 in |
1 in |
13.875 x 16.375 in |
| 11 x 14 in |
2.5 each side |
0.125 in |
1.25 in |
18.375 x 21.375 in |
| 16 x 20 in |
3 each side |
0.125 in |
1.5 in |
24.875 x 28.875 in |
Formula Used
Visible opening width = Artwork width - 2 x overlap + 2 x reveal
Visible opening height = Artwork height - 2 x overlap + 2 x reveal
Mat outside width = Visible opening width + left border + right border
Mat outside height = Visible opening height + top border + bottom border
Rabbet size = Mat outside size + 2 x fitting allowance
Glass cut size = Rabbet size - 2 x glass clearance
Outside frame size = Rabbet size + 2 x frame face width
Moulding length = 2 x outside width + 2 x outside height + 4 x miter waste
How To Use This Calculator
Enter the artwork width and height first. Use the same unit for every field.
Add mat borders for each side. Use equal borders for simple layouts.
Enter overlap when the mat should cover the artwork edge. Enter reveal when the artwork should float inside the opening.
Add frame face width, fitting allowance, glass clearance, and miter waste. Press calculate to view the result above the form.
Use the CSV button for spreadsheet records. Use the PDF button for framer notes or client approval.
Why Frame Sizing Matters
A picture frame looks simple, yet each layer needs a clear size. Artwork, mat board, glazing, backing, and moulding all meet at the rabbet. A small error can create tight corners, exposed paper, or wasted material. This calculator keeps those parts aligned before cutting begins.
Good planning also protects the image. The mat opening should cover the artwork edge slightly. This overlap hides uneven paper edges. It also keeps the sheet from slipping forward. The visible opening is therefore smaller than the full artwork size.
Understanding Mat Borders
Mat borders shape the visual balance. Equal borders give a clean studio look. A wider bottom border can make framed art feel grounded. Unequal borders are useful for signatures, title blocks, or printed captions. The calculator accepts separate left, right, top, and bottom borders, so advanced layouts are easy to test.
The mat outside size becomes the working size for glass and backing. It is based on the visible opening plus the selected borders. A fitting allowance then adds space inside the frame rabbet. This small clearance helps the stack fit without bowing.
Frame And Glass Planning
Frame face width affects the finished outside dimension. A narrow moulding keeps attention on the picture. A wider moulding adds presence and can suit large prints. The outside size is the rabbet size plus the moulding face on both sides.
Glass should normally be cut slightly smaller than the rabbet size. This allowance helps during assembly. It also reduces edge stress caused by tight fitting. Backing can follow the same size when the frame design allows it.
Using Results In A Workshop
Use the results as a cutting checklist. Confirm the unit first. Then review visible opening, mat outside size, rabbet size, glass size, and outside frame size. Save a CSV copy for shop notes. Download the PDF when sharing details with a framer.
Always measure the actual artwork. Printed labels can be wrong. Check moulding rabbet depth, too. Thick mats, spacers, or foam boards may need more depth. When the frame is valuable, make a test fit before final assembly. This habit prevents expensive recuts and improves final presentation. Record final assumptions whenever material suppliers use different sizing rules locally.
FAQs
What is a picture frame size calculator?
It estimates the visible opening, mat outside size, rabbet size, glass cut size, and finished frame size from your artwork and border measurements.
Should I enter artwork size or visible image size?
Enter the full artwork size. The calculator subtracts mat overlap and adds any reveal gap to find the visible opening.
What is mat overlap?
Mat overlap is the amount of mat board that covers each artwork edge. It hides paper edges and helps hold the artwork in place.
What is a reveal gap?
A reveal gap is open space around the artwork. It is useful for float mounts or designs where the artwork edge should remain visible.
What does rabbet size mean?
Rabbet size is the inside frame space that holds the mat, glass, and backing. It must be slightly larger than the mat outside size.
Why is glass clearance needed?
Glass clearance makes the glass cut slightly smaller than the rabbet. This helps prevent tight fitting and edge pressure during assembly.
Can I use centimeters or millimeters?
Yes. Select the unit first, then enter every measurement in that unit. Do not mix inches, centimeters, and millimeters in one calculation.
Does the calculator include miter cutting waste?
Yes. Enter miter waste per frame piece. The calculator adds four waste allowances to the total moulding length per frame.