Finding the perfect picture frame often feels like a balancing act between protecting your artwork and achieving a polished, gallery-worthy display, especially when introducing the visual buffer of a mat board. To get the sizing exactly right, you must measure the precise dimensions of your artwork’s visible area, calculate the desired mat board border width, and account for the necessary overlap where the frame’s inner lip holds the assembly in place. A single millimeter of error can cause artwork to slip, buckle, or be awkwardly cropped behind the glazing. By mastering a few straightforward measuring techniques and mathematical calculations, you can confidently select or order the ideal frame size for any print, photograph, or canvas.
Whether you are preparing a gallery wall for a residential living room or framing a single statement piece, precision at the start saves time and prevents the cost of returning ill-fitting materials. Taking the time to understand how frame components interact ensures that your art remains secure, flat, and beautifully preserved over time.
What tools do you need to measure artwork and frames accurately?
To measure artwork and frames with high precision, you need a rigid steel ruler, a metal tape measure, and a flat, clean surface. These tools prevent the flexing and stretching common with softer measuring instruments, ensuring your numbers remain accurate down to the millimeter. Using the wrong tools is one of the most common sources of error in DIY framing projects.
Flexible sewing tapes made of cloth or plastic are highly susceptible to stretching over time, which can easily introduce a discrepancy of several millimeters over longer distances. Standard plastic or wooden school rulers are often too short for medium-to-large prints, forcing you to slide the ruler along the paper—a practice that almost always introduces cumulative measurement errors. A high-quality steel ruler of at least 24 inches (or 60 centimeters) is ideal because it lies perfectly flat, does not bend, and features highly precise, etched increments. For larger pieces, a heavy-duty metal tape measure with a locking mechanism is the preferred choice.
In addition to measuring devices, a metal T-square or L-square is incredibly helpful for verifying that the corners of your artwork are perfectly square. Over time, paper prints or canvases can warp or be cut slightly out of alignment. Checking the corners ensures that your calculated frame dimensions will accommodate the actual shape of the piece.
Before you begin, prepare a clean, dust-free, and well-lit work surface. Lay down a clean sheet of acid-free paper or a soft, lint-free microfiber cloth to protect the face of your artwork from scratches, oils, or debris. Ensure you have bright, direct overhead lighting so you can clearly read the increments on your measuring tool without straining or guessing.
How do you measure artwork for a picture frame without a mat board?
Measuring artwork for direct framing without a mat board requires finding both the exact dimensions of the visible image and the total physical size of the paper or canvas. You will use these two measurements to decide whether the frame’s inner lip should overlap the image itself or sit flush against a blank margin. Direct framing is a clean, modern approach, but it leaves little room for error since the frame edge directly borders the art.
First, measure the exact image size. This is the area containing the actual printed or painted subject matter, excluding any blank margins or borders. Use your steel ruler to measure the width and height of this area at two different points to ensure the print is uniform. If you want the frame to border the image directly, this measurement will dictate your viewing window.
Second, measure the total paper or canvas size. This is the entire physical sheet from edge to edge, including any white margins, signatures, or deckled (rough, torn) edges. If the artwork has a beautiful deckled edge that you wish to showcase, you will likely want to “float” the artwork on top of a backing board rather than tucking the edges under a frame lip. In this scenario, your frame size will need to be significantly larger than the paper size to leave an attractive border of backing board visible around the entire sheet.
Third, decide whether to show the entire paper surface or crop the edges based on the layout. If the print has plain white margins that contain no signature or numbering, you can choose to let the frame’s inner lip overlap these margins, hiding them completely. However, if the artist’s signature or print number sits close to the bottom edge of the image, you must ensure the frame lip does not cover these important details. Write down both the image dimensions and the total paper dimensions clearly, labeling them to avoid confusion later.
How do you calculate picture frame sizing when adding a mat board?
Calculating frame sizing with a mat board involves subtracting a small overlap from your artwork’s dimensions to find the inner mat opening, then adding your desired border widths to determine the outer mat board size. The outer dimensions of your mat board will correspond exactly to the inner size of the frame you need to purchase. Mat boards provide a professional, museum-like aesthetic while keeping the artwork from touching the glass, which prevents moisture damage.
To find the inner mat opening, you must determine how much of the artwork you want the mat to cover. The opening must be slightly smaller than the artwork itself so the mat board can rest on top of the edges and hold the piece in place. For a standard print, subtracting 1/4 inch (about 6 millimeters) from both the width and height of the image area is a reliable standard. This creates a 1/8-inch overlap on all four sides, securing the paper without covering too much of the design.
Next, choose the mat board border width for aesthetic balance. The border width is a matter of personal preference, but standard borders typically range from 1.5 inches to 3 inches for small to medium art, and can go much wider for dramatic effect. A helpful design technique is “bottom-weighting,” where the bottom border of the mat is cut slightly wider than the top and sides (for example, a 2-inch border on the top and sides, and a 2.5-inch border on the bottom). This offsets an optical illusion that makes centered artwork appear as though it is sinking toward the bottom of the frame.
To calculate the final outer mat board dimensions, use the following formulas:
- Total Mat Width = Inner Mat Opening Width + Left Border Width + Right Border Width
- Total Mat Height = Inner Mat Opening Height + Top Border Width + Bottom Border Width
For example, if you have an 8×10-inch photo and want a uniform 2-inch mat border on all sides:
- Your inner mat opening will be 7.5 x 9.5 inches (accounting for a 1/4-inch total overlap to hold the photo).
- Your total mat width will be: 7.5 inches + 2 inches (left) + 2 inches (right) = 11.5 inches.
- Your total mat height will be: 9.5 inches + 2 inches (top) + 2 inches (bottom) = 13.5 inches.
In this scenario, you would need to purchase a frame with an internal opening of exactly 11.5 x 13.5 inches, or opt for custom cutting if standard sizes do not match.
How much overlap should the frame or mat board have over the artwork?
A standard mat board opening should overlap the artwork by 1/8 inch to 1/4 inch on every side to secure the piece without obscuring critical visual details. Similarly, the frame’s inner lip, known as the rabbet, must overlap the outer edge of the mat board or backing board by about 1/8 inch to keep the entire assembly inside the frame. Understanding these overlaps is crucial to preventing your artwork from falling through the openings.
For small to medium prints on flat paper, a 1/8-inch overlap on all four sides of the mat opening is generally sufficient. This minor overlap is barely noticeable but provides enough surface area to apply acid-free mounting tape to the back of the mat, securing the artwork in place. For larger prints, particularly those on heavier paper stocks that may expand or contract with changes in humidity, a 1/4-inch overlap on all sides is highly recommended. This larger margin accommodates minor shifts in the paper over time without exposing the edges of the print.
When it comes to the frame itself, the rabbet is the recessed groove on the back inner edge of the frame molding that holds the glass, mat, artwork, and backing. The width of this lip is typically 1/4 inch. Because the frame lip covers this outer edge, the visible opening of the frame from the front will be slightly smaller than the ordered frame size. For instance, an 11×14-inch frame will have an actual front viewing window of approximately 10.5 x 13.5 inches. You do not need to adjust your mat calculations for this, as standard mat boards are already designed to account for this frame overlap.
If you are framing thick or heavy materials, such as a stretched canvas or a wood panel, standard mat boards are rarely used. Instead, you must focus on the depth of the frame’s rabbet. The rabbet depth must equal or exceed the total thickness of the canvas stretcher bars or panel. If the rabbet is too shallow, the artwork will protrude from the back of the frame, making it impossible to secure the backing points or hang the frame flush against the wall.
How do you determine the final outer frame dimensions to purchase?
To determine the correct frame size to purchase, match the frame’s internal opening size exactly to the outer dimensions of your mat board or un-matted artwork. The overall outer footprint of the frame on your wall will then depend on the width of the frame molding you choose. When shopping for frames online or in a store, the size listed on the label always refers to the internal opening (the rabbet-to-rabbet measurement), not the outer edge of the wood or metal border.
If your calculated outer mat dimensions match a standard industry size, you can easily purchase a ready-made frame. Common standard sizes include 8×10, 11×14, 16×20, and 24×36 inches. If your calculations yield an unusual size—such as the 11.5 x 13.5-inch example calculated earlier—you have two primary options. You can order a custom-sized frame built to those exact internal dimensions, or you can adjust your mat border widths slightly so that the outer mat dimensions align with a standard, widely available frame size.
To understand the total wall footprint and visual weight of the framed piece, you must account for the frame molding width. If you choose a delicate, modern metal frame with a molding width of 0.5 inches, an 11×14-inch frame will have an outer footprint of 12×15 inches. If you choose a rustic, wide wooden frame with a molding width of 2.5 inches, that same 11×14-inch frame will occupy a wall space of 16×19 inches. Calculating this total footprint is essential for planning gallery walls and ensuring the frame does not crowd nearby light switches, outlets, or architectural features.
For larger or heavier frames, always verify the wall mounting hardware and installation environment. Heavy wood frames, thick glazing, and large mat boards create suspended loads that require secure mounting. Ensure you use sturdy D-rings, heavy-duty picture wire, or French cleats anchored directly into wall studs or appropriate drywall anchors. For exceptionally heavy or valuable installations, consulting a professional installer is a safe way to prevent damage to your walls and artwork.
What common mistakes should you avoid when measuring for picture frames?
The most common mistakes when measuring for picture frames include confusing the frame’s outer border dimensions with its inner rabbet size and failing to account for the depth of the artwork assembly. Avoiding these errors prevents buying frames that are too small to hold your pieces or too shallow to accommodate your backing and glazing. A systematic approach to measuring will save you from frustrating mismatches.
One frequent error is measuring the outside edge of an existing frame to determine what size mat board or print will fit inside it. Because frame moldings vary widely in width, the outer dimension tells you nothing about the internal capacity. Always measure the rear opening where the glass, mat, and backing board actually sit. This is the only measurement that dictates compatibility.
Another common oversight is ignoring the cumulative thickness of your framing materials. A standard frame’s rabbet depth is often around 1/2 inch. If you plan to use a double mat board, a thick piece of textured watercolor paper, a mounting board, and a sturdy backing board, the total thickness might exceed the depth of the frame’s lip. When this happens, the backing points cannot be secured into the frame channel. Always check the rabbet depth specification of the frame before purchasing, especially when framing thick textiles, heavy boards, or multi-layered mats.
Finally, avoid the mistake of measuring your available wall space first and forcing your artwork to fit that arbitrary size. Always start with the physical dimensions of the artwork itself. Calculate the necessary mat borders and frame overlaps outward from the art, determine the final outer footprint of the frame, and only then verify if that footprint fits safely and aesthetically on your wall. This inside-out approach ensures that the artwork remains the focal point and is preserved in a structurally sound, perfectly proportioned enclosure.
Community discussion
Share your experience or ask a question. Comments are reviewed before publication.