Picture Frame Size Calculator
Calculate the frame size needed for your photo with a mat border.
Enter photo dimensions and mat width to find the right frame.
Picture frame sizing and matting involve three distinct measurements: the artwork size, the mat (passepartout) opening and border, and the frame’s rabbet (recess) size. Getting these right ensures the artwork is properly presented without covering important content or leaving unintended gaps.
Frame rabbet size formula: Frame Inner Dimension = Artwork Width (or Height) + 2 × Mat Border Width − 2 × Mat Overlap
Standard mat overlap onto artwork: 0.25 inches per side (to hide the edge of the artwork/paper)
Mat opening (window) size: Mat Window = Artwork Dimension − 2 × Overlap
For a 5″ × 7″ photo with 0.25″ overlap per side: Mat window = (5 − 0.5) × (7 − 0.5) = 4.5″ × 6.5″
Mat border width — design guidelines:
- Narrow border (minimal): 1.5–2 inches
- Standard border: 2–3 inches
- Gallery-style: 3–4+ inches
- Bottom-weighted mat: bottom border 0.5–1 inch wider than top and sides — optically compensates for the eye’s tendency to perceive even borders as top-heavy
Frame glass/acrylic size: Glass = Frame Inner Dimension (same as rabbet opening — glass fits flush inside the rabbet lip)
Matboard quantity — multi-opening mats: Count the mat windows and border areas, then add 10% for cutting waste.
Backing board: Cut to same dimensions as glass. Use acid-free foam core or matboard for archival framing.
Archival vs. standard framing:
- Archival (museum) quality: Acid-free mat, UV-filtering glass, no adhesive touching artwork
- Standard: Chipboard mat, regular glass — fine for decorative prints, not for original art or photographs meant to last decades
Common frame sizes (US standard): 4×6, 5×7, 8×10, 8.5×11, 11×14, 16×20, 18×24, 20×24, 24×36 inches — buy standard sizes to avoid custom framing costs.
Worked example: Original watercolor: 9″ × 12″. You want a 3″ mat border on all sides, with 0.25″ overlap on artwork.
- Mat window opening: (9 − 0.5) × (12 − 0.5) = 8.5″ × 11.5″
- Frame inner dimension: (9 + 6 − 0.5) × (12 + 6 − 0.5) = 14.5″ × 17.5″
- This is close to the standard 16×20 frame (extra mat border absorbs the difference)
- Custom frame cost (16×20): $40–$120 retail; $200–$600 at custom framing shops for archival