How to Size Picture Mats and Frames

Picture border mats are measured and then cut to size.

Mat borders and picture frames are sized by measuring a picture and using its dimensions to calculate how large the border and frame should be. After the picture and frame are measured, the mat is cut to size. Mat borders are cut with a mat cutting machine, which consists of a flat table or board with a long, straight blade guard and a cutting blade that slides along a grooved track located on the edge of the board. The blade guard ensures that the cutter makes straight, even cuts with edges that are slightly beveled or angled.

Things You'll Need

• Ruler
• Scrap paper
• Pencil
• 6-ply 8-by-10-inch mat board
• T-square
• Bevel mat cutter
• 6-by-12-inch scrap mat board or mat cutter slip sheet

Instructions

1. Measure 1/8-inch in from the outside edges on all four sides of the picture. At the 1/8-inch point, again measure all four sides of the picture. Write the measurements of the sides down and label them "inner border dimensions" on your scrap piece of paper. These are the measurements for the square hole or window of the border mat where the picture will be inserted.

2. Decide how big you want the border of your picture to be. The border fills in the area between the picture and the edges of the frame. Mat borders are usually equally sized on the top, left and right sides of the border, with an extra 1/4 to 1/2 inch on the bottom border. This extra space on the bottom weighs down the mat and holds the picture in place when it is hung on the wall. The mat borders should be no narrower than 2 inches wide or they won't hold the picture in the frame and it will fall behind the mat.

3. Add the width of the border to the inner border dimensions of the picture to determine the size of picture frame needed. For an 8-by-10 picture with a border that is 2 inches wide on the top, right and left sides and 3 inches wide on the bottom, the 2-inch borders are added to the measurements of the top, left, and right sides of the picture and the 3 inches are added to the bottom measurement.

4. Transfer the border dimension measurements to the back of the border mat and make a mark with a pencil. Use the T-square to measure and draw the inner border dimensions onto the back of the border mat with a pencil, using the border dimension measurements as a guide. Over-extend the lines by 1 inch at the corners to make marks that provide a better visual indication of where you need to start and stop cutting the mat.

5. Place 6-by-12-inch piece of scrap mat board or a mat cutter slip sheet down on the mat cutter with the 12-inch side running along the length of the cutter board, where the long straight-edged blade guide is located. Set the border mat face --- the colored side --- down onto the scrap mat board or mat cutter slip sheet with the pencil drawing of the picture window facing up.

6. Adjust the mat cutter's blade depth to accommodate a 6-ply mat board. Adjust the mat cutter blade guide to the border's width. Hold the blade of the cutter just before the start of the bottom corner of the first side of the drawn window that you wish to cut with the blade tip touching the start of the line.

7. Apply even pressure onto the cutter and push it forward, moving the blade up the mat and away from you as you cut the first edge of the border window. The cutter should be flush against the cutting guide at all times as you make the cut. Cut one side of the border at a time. Gently push the window piece out of the border once you have cut it out.

Tips & Warnings

• If you don't have a mat cutter, you can set the mat board on a table lined with thick cardboard. Place a long metal T-square on the pencil lines and carefully cut the window out with a sharp utility knife, using the straight edge of the T-square as a guide for the blade to ensure an even, straight cut on the mat.

• If you are planning to hang the picture on the wall higher than eye level, which is around 5 to 6 feet high, make the bottom border an extra 1 inch wider. An evenly measured border will look uneven when hung on the wall at that height. The extra width on the bottom of the border makes it appear even when the picture is hung. This is caused by an optical illusion that occurs when you are looking up at a picture instead of straight at it.

• Take care when handling sharp mat cutter blades as they can cause serious injury. Be mindful at all times of where you are placing your hands when using a mat cutter. If you are not careful you may accidentally cut deeply into your hand.

• Always cut away from yourself when using a knife of any kind.

References

• Art Supply: How to Cut a Basic Mat
• Framing 4 Yourself: How to Picture Frame: Step One: Measuring
• Metro Frame: Mat Calculations
• Picture Framing Magazine: How to Effectively Cut Mat Borders
• Altos EZ Mat: Cutting a Basic Single Mat
• Logan Graphic: Platinum Edge Mat Cutter

Resources

• Logan Graphic: Basic Measuring for Picture Framing
• Dick Blick: Calculating Border Sizes