How to Use the Picture Frame Size Calculator
Our picture frame size calculator makes it easy to find the exact dimensions for any custom or standard picture frame. Whether you're framing a treasured photograph, a piece of fine art, or a child's drawing, simply enter a few measurements and get instant, accurate results. Here's how:
- Choose your unit - Select inches (in) or centimeters (cm) using the toggle at the top of the calculator.
- Enter picture dimensions - Input the width and height of your photo or artwork. You can also click one of the preset size buttons (4×6, 5×7, 8×10, etc.) to auto-fill common sizes.
- Set your border (molding) width - This is the width of the decorative frame molding - the wooden, metal, or plastic strip that forms the visible border.
- Add mat size (optional) - Enter mat width and height to add a mat between the picture and the frame. Mats improve the appearance and protect the artwork.
- Adjust advanced settings (optional) - Set the rabbet width (the groove inside the frame) and fudge factor (a small tolerance for easy fitting).
- Read your results - The calculator instantly shows inner frame dimensions, outer frame dimensions, total molding length, and a visual frame preview.
Picture Frame Calculation Formulas Explained
Understanding the math behind picture frame measurements helps you verify results and make custom frames with confidence. Here are the formulas our calculator uses:
Outer Frame Dimensions
The outer dimensions are the overall size of the finished frame from edge to edge:
Outer Height = Picture Height + (Mat Height + Border Width) × 2
Inner Frame Dimensions (Rabbet Opening)
The inner dimensions are the actual opening of the frame - the viewable area where your picture shows through:
Inner Height = Picture Height + (Mat Height − Rabbet Width) × 2 + Fudge Factor × 2
Total Molding Length (Frame Perimeter)
The molding length tells you how much frame material you need to buy to build all four sides:
Note: This calculation assumes standard 45° miter cuts at all four corners, which is the most common framing technique.
What Is a Picture Frame Mat?
A picture frame mat (also called a mount or mat board) is a flat border placed between your artwork and the frame glass. Mats serve several important functions:
- Aesthetic: Adds a visual "breathing room" around the image, directing the viewer's eye to the artwork.
- Protection: Keeps the picture surface from touching the glass, preventing moisture damage and sticking.
- Archival: Acid-free mat boards protect valuable artwork or photographs from deterioration over time.
- Sizing: Allows a smaller picture to fit neatly inside a larger standard-size frame.
For standard framing, a mat width of 2–3 inches on all sides is a common starting point. For artwork with more visual weight, wider mats of 3–4 inches can create an elegant gallery feel.
What Is Frame Molding Width?
The frame molding (also spelled moulding) is the decorative strip of material that forms the frame's visible border. It wraps around the perimeter of the picture and gives the frame its distinctive style - whether flat, rounded, ornate, or modern. The molding width is measured from the outer edge of the frame to the inner rabbet edge.
Common molding widths range from a slim 0.5 inch for minimalist frames to 3–4 inches for ornate gallery-style frames. Most everyday picture frames use 1–2 inch molding widths.
What Is the Rabbet Width?
The rabbet (or rebate) is the stepped groove or lip on the inner back edge of the frame molding. This groove is what holds the glass, mat board, artwork, and backing board in place inside the frame. The rabbet width is typically 0.25–0.5 inches for standard frames.
When calculating inner frame dimensions, the rabbet reduces the visible opening size - so the inner frame opening will be slightly smaller than the outer molding edge, but it's designed to hold the artwork securely.
Picture Frame Size Tips & Best Practices
- Always measure the art, not the paper: If you're framing a print, measure the image area you want to show, not the full paper sheet.
- Add a fudge factor: A small tolerance of 0.05–0.1 inches ensures your picture slides in without forcing.
- Use acid-free materials: For valuable photos or artwork, use acid-free mat board and UV-protective glass.
- Consider visual weight: Heavier, more complex images benefit from wider mats to prevent the image from feeling cramped.
- Standard sizes save money: Whenever possible, size your prints to fit standard frame sizes to avoid custom framing costs.
- Measure twice, cut once: Double-check all measurements before cutting molding material or mat board.
Frequently Asked Questions
To calculate the correct picture frame size, start with your picture's width and height, then add twice the mat size and twice the molding (border) width to each dimension. For example, an 8×10 inch photo with a 2-inch mat and 1.5-inch molding on each side gives an outer frame size of 8+(2+1.5)×2 = 15 inches wide and 10+(2+1.5)×2 = 17 inches tall. Our calculator above does all this math instantly.
The most common standard picture frame sizes in the US are 4×6 inches, 5×7 inches, 8×10 inches, 11×14 inches, 16×20 inches, and 24×36 inches. These align with standard photo print sizes. European standard sizes follow the A-series paper dimensions: A4 (21×29.7 cm), A3 (29.7×42 cm), and so on. Sizing your artwork to fit these standard sizes will save money compared to custom framing.
A standard mat border width is typically 2–3 inches for most artwork. For a more elegant, gallery-style look, use wider mats of 3–5 inches. A useful design trick is to make the bottom mat border slightly wider (by 0.5–1 inch) than the top and sides - this creates an optically balanced appearance since the eye tends to perceive centered content as appearing slightly high.
The total molding length needed equals the perimeter of your outer frame: (Outer Width + Outer Height) × 2. For example, if your outer frame is 15 × 17 inches, you need (15 + 17) × 2 = 64 inches of molding. In practice, always buy a little extra (10–15%) to account for waste from miter cuts at each corner.
The outer frame dimensions are the total external size of the frame from one edge to the other - what you'd measure if you placed the frame face-down and measured the wooden border. The inner frame dimensions (also called the rabbet opening) are the actual opening inside the frame where your picture, mat, and glass sit. The inner dimensions are always smaller than the outer dimensions by the rabbet width on each side.
Yes! Our picture frame size calculator fully supports both inches and centimeters. Simply click the "Centimeters (cm)" toggle at the top of the calculator to switch units. All inputs, outputs, and the visual diagram will update to display values in centimeters. This is ideal for European standard frame sizes like A4, A3, and other metric dimensions.