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How to Figure the Right Length(s) of Moulding to Make Your Frame

How to figure the right lengths of mouldings

Follow these steps to learn how to figure the right lengths of moulding…

1.) Decide on an Appropriate Width of Moulding

The width of the moulding is the distance across the face, the part that is facing outward when the frame is hanging on the wall. As a rule of thumb consider frame widths of 3/4″ to 1-1/4″ for frame sizes from 8″x10″ to 15″x19″. Consider frame widths of 1.5″ to 2-1/4″ for frame sizes from 16″x20″ to 23″x25″. Consider frame widths 2-1/2″ or larger for frame sizes 24″x36″ and larger. Note: This is just a rule of thumb and aesthetic considerations should guide you in your choice.

2.) Select the Desired Style of Moulding

Look over the selections on our website and choose the frame style you want, make note of the width of the moulding you have chosen.

3.) Determine the Appropriate Length(s) of Moulding Needed to Make Your Frame.

Step 1: Add together the four sides of the frame you wish to make. For example: To make a 16″x20″ frame, figure 16+16+20+20= 72″.

Step 2: Multiply the width of the moulding by 8, and add that to the sum. For example: To make a 16″x20″ frame using a 2″ wide moulding, multiply 2″ x 8 = 16″, then add 16″ to 72″. ie., 16″+ 72″ = 88″. For more on this, see the FAQ’s below.

Step 3: Add a quarter inch to the total to allow for some wiggle room in the frame recess so the stack of matboard, foamboard and glazing doesn’t fit too tightly. For example: 88″ + 1/4″ = 88-1/4″. For more on this, see the FAQ’s below.

Step 4: At this point you know the length of the moulding in inches, to discover the length of the moulding in feet, divide the length in inches by 12. For example: 88-1/4″÷12= 7.35 feet.

Step 5: Select the best length or combination of lengths to make your frame. Remember, it is always better to have more than you need. To cut the above size, an 8 foot length of Moulding (Cut to 4 ft and 4 ft) would be appropriate. For more on this, see the FAQ’s below.

Note: When the necessary footage requires an exact (or nearly exact) length, the wise framer defaults to the next longer length, allowing for a little extra room.


Why are you Adding the Width of the Moulding times 8 to the Frame Size?

When building a picture frame, you will miter the ends of each section to create the angles that, when fitted together, will form a corner. Each one of the eight miters needed to make the four corners will be equivalent in the length to the width of the frame across its face. So if the frame is 1″ wide, you will need enough moulding to make the four sides as well as 1″ x 8 to account for the miters. If the frame is 2″ wide, you will need 2″ x 8 = 16″ to account for the miters.

Why are you Adding 1/4″ to the Length to Account for “Wiggle Room”?

If you want to frame something that is 16″x20″, you could make the frame exactly 16″x20″, but then each of the frame’s components would have to be cut perfectly to fit into the frame. If they are off by just a hair, they won’t fit. In picture framing parlance, the wiggle room we build into the frame is called the “allowance”, and every picture framer builds an allowance into his or her frame. Typically the allowance is an additional 1/16″ along each side. To have enough moulding to build an addiitonal 1/16″ allowance into the frame, you are going to need (4) x 1/16″ = 1/4″.

Why Will (2) 4 Foot Lengths be Preferable When Making a Picture Frame 16″x20″ that is 2″ Wide?

Consider that you will need two sticks of 20″ (16+2+2) , and two sticks of 24″ (20″+2″+2″). Now, if you attempt to take both 24″ sides out of a single 48″ (4 ft) length, you will be cutting it too close and not have enough for the allowance. The better approach is to take one of the 24″ sides and one of the 20″ sides out of each 48″ length. This is a total of 44-1/8″ per 48″ length, leaving plenty of stick to work with.



    1. I apologize for the delay – your note was caught in our spam folder. The piece of plexiglass depends on the size of the artwork you are framing. If you are framing a 36″ x 36″ piece of art, you would need a 36″ x 36″ piece of acrylic.


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