Enter your dimensions and options, then select Calculate to see frame opening, cut sizes, outer size, moulding length, material costs, and a fit check.
- For optical centering, make the bottom mat border slightly larger than the top.
- Subtract a small allowance from glazing and backing to ensure an easy fit.
- Kerf and waste allowances vary by saw and workflow; measure your own process.
A Picture Frame Calculator helps you translate a print size into the precise measurements needed for the mat window (the opening), the exterior mat size, the glass size, and the frame interior opening. Whether you are framing photography, certificates, posters, or artwork, a calculator reduces guesswork, prevents costly re-cuts, and keeps your presentation consistent and professional. This guide explains the key inputs, the formulas behind common calculators, and practical allowances used by framers.
Key Inputs You Will Enter
- Print size (width × height): the actual image sheet size, such as 8 × 10 in or 210 × 297 mm.
- Reveal (overlap): how much of the print the mat covers on each side to keep it from slipping. Typical reveals are 1⁄16–1⁄8 in (2–3 mm).
- Mat borders: uniform borders (e.g., 2 in all around) or bottom-weighted (e.g., +0.5 in on the bottom).
- Frame allowance: a small oversize added to glass/mat/backing dimensions (often 1⁄16 in) so the stack fits into the frame rabbet.
- Stack thickness: glazing + mat + artwork + backing; verify it is less than rabbet depth.
Core Formulas Used by a Picture Frame Calculator
Given a print of Wp × Hp, reveal r, uniform mat border b, and fit allowance a:
| Quantity | Formula | Notes |
|---|---|---|
| Mat window (opening) | Wopen = Wp − 2rHopen = Hp − 2r |
Opening is slightly smaller than the print so edges are hidden and held in place. |
| Exterior mat size | Wmat = Wp + 2bHmat = Hp + 2b |
For bottom-weighted mats, add the extra only to H. |
| Frame interior opening | Wframe = Wmat + aHframe = Hmat + a |
Apply small positive allowance so the unit drops into the rabbet cleanly. |
| Glass / backing size | Same as frame interior opening |
Order or cut glazing and backing to the frame interior dimensions (with allowance). |
Common Print Sizes and Typical Calculator Outputs
The table below assumes a 1⁄8 in reveal and a uniform 2 in mat border. The frame allowance used is 1⁄16 in.
| Print Size (in) | Mat Window (in) | Exterior Mat Size (in) | Glass & Frame Interior (in) |
|---|---|---|---|
| 5 × 7 | 4.75 × 6.75 | 9 × 11 | 9.06 × 11.06 |
| 8 × 10 | 7.75 × 9.75 | 12 × 14 | 12.06 × 14.06 |
| 11 × 14 | 10.75 × 13.75 | 15 × 18 | 15.06 × 18.06 |
| 16 × 20 | 15.75 × 19.75 | 20 × 24 | 20.06 × 24.06 |
| 18 × 24 | 17.75 × 23.75 | 22 × 28 | 22.06 × 28.06 |
Recommended Mat Border Widths
Choose borders that balance the composition and keep the eye on the artwork. Bottom-weighting subtly corrects visual gravity when hung.
| Frame Category | Typical Frame Size | Uniform Border | Bottom-Weighted Option |
|---|---|---|---|
| Small | 8 × 10 to 11 × 14 | 1.5–2 in | Add +0.25–0.5 in to bottom |
| Medium | 16 × 20 to 18 × 24 | 2–3 in | Add +0.5–0.75 in to bottom |
| Large | 20 × 24 to 24 × 36 | 3–4 in | Add +0.75–1 in to bottom |
Worked Example
You have an 8 × 10 in print, want a 2 in uniform mat border, a 1⁄8 in reveal, and a 1⁄16 in fit allowance.
If your rabbet depth is 3⁄8 in and your stack is 2 mm glass + 1.4 mm mat + 2.5 mm foam board (≈5.9 mm total), you have comfortable clearance. Always check the depth against the stack.
Stack Thickness Planning
| Material | Typical Thickness | Notes |
|---|---|---|
| Glazing (glass) | 2.0–2.5 mm | Standard picture glass; acrylic is lighter and 2.0–3.0 mm. |
| Mat board | 1.4–1.6 mm | Conservation boards often around 4‑ply (~1.4 mm); 8‑ply is ~2.8–3.2 mm. |
| Artwork + hinge | 0.2–0.5 mm | Varies by paper stock and hinge method. |
| Backer (foam/core) | 2–5 mm | Use archival backers for long‑term display. |
| Total (example) | ~6 mm | Fits well in 9–10 mm rabbet depth. |
Aspect Ratio and Cropping
A calculator also flags aspect ratio mismatches. A 4:5 print (8×10) set into a 2:3 frame (12×18) requires either custom matting or cropping. To avoid unintended crops, select a frame whose interior aspect ratio matches your print, or use a mat that adapts the ratio while keeping the artwork intact inside the window.
Metric vs Imperial
You can work entirely in millimeters if you prefer. The formulas are identical; just keep the same units throughout. A handy mental conversion is 1 in = 25.4 mm; 1⁄16 in ≈ 1.6 mm; 1⁄8 in ≈ 3.2 mm.
Quality and Conservation Considerations
- Use acid‑free, lignin‑free mats and backers for valuable pieces.
- Prefer UV‑filtering acrylic or glass in bright rooms to slow fading.
- Float mounting requires spacers; include their thickness in your stack plan.
- Do not over‑tighten points or tabs; gentle pressure prevents buckling.
Frequently Asked Questions
| Question | Concise Answer |
|---|---|
| How much reveal should I use? | 1⁄16–1⁄8 in (2–3 mm) per side is typical; textured papers may need a touch more. |
| Do I add the allowance to the mat window? | No. The window is smaller than the print (by 2 × reveal). Add the allowance to glass, mat exterior, and backing. |
| What if I want bottom‑weighted borders? | Increase only the bottom mat border by your chosen amount (e.g., +0.5 in). Exterior mat and frame height increase accordingly. |
| Can I frame without a mat? | Yes. Set glass and backing to the print size plus allowance. Consider spacers to keep artwork off the glazing. |
| How precise do cuts need to be? | Stay within ±1⁄32 in (±1 mm) for clean fits. The 1⁄16 in allowance provides breathing room. |
Checklist Before You Cut
- Confirm print size with a ruler, not the label.
- Decide reveal, borders (uniform or bottom‑weighted), and allowance.
- Verify aspect ratio compatibility or plan for a custom mat.
- Add up stack thickness and compare to rabbet depth.
- Record final cut list: mat window, exterior mat, glass/backing, and frame opening.
With these formulas and tables, a Picture Frame Calculator becomes a reliable roadmap from print to finished frame. Use the example values as a starting point, adjust for your materials, and you will achieve repeatable, gallery‑grade results.