The direct answer: measure the outside of the frame, add the thickness of the corner protection to both the length and the width, add the hanging hardware to the depth, and that is your internal box size. The print size on the front of the frame is not part of the calculation.
Why the print size misleads people
Standard print sizes such as 8 x 10, 11 x 14 and 16 x 20 in describe the image, and the moulding wraps around all four sides of it. A narrow moulding adds a little. A wide gallery moulding with a mat can add several inches per side. Since the moulding width varies across your own range, two frames sold as the same size can need two different boxes.
Four questions that settle the size
Glass or acrylic?
Glass is heavy and breaks at the corner, so it needs corner protectors, a face barrier and a board that resists bending. Acrylic is lighter and scratches instead of breaking, so the priority moves to a face barrier and a snug fit. The two can share a dieline, but they rarely share a board spec.
What is on the back?
A hanging wire strung between D rings sits proud of the backing board, and an easel stand sits proud further still. Measure to the highest point on the back, not to the backing board, or the lid will not close flat.
One frame or several?
Multipacks need a divider between each frame, and each divider adds to the internal depth. Pack them back to face rather than face to face, so no two glazed surfaces are pressed together with only board between them.
Is it going in the post on its own?
A frame posted individually takes more handling abuse than one in a palletised retail delivery. That pushes you toward a fold-around style that locks tight, or a telescoping two piece where the lid reinforces the edges.
A worked example
Take an 11 x 14 in print in a moulding 2 in wide. The outer frame measures about 15 x 18 in. Add corner protectors 1/2 in thick at each corner and the internal size becomes roughly 16 x 19 in. If the frame is 1 in deep and the wire and D rings add another 1/4 in, the internal depth is about 1.25 in before you add a face pad. That is how a print described as 11 x 14 ends up in a box closer to 16 x 19 in.
Ordering
The minimum is 100 boxes, priced from about $0.48 per unit at bulk volumes and confirmed on your written quote. The die, the plates, design support, US shipping and a digital proof before printing are included, so a box drawn to your own moulding is not a premium over a near standard size. Production is quoted per product in three lanes, rush (expedited production plus air freight), standard (air) and cost saver (sea), from about 7 business days, plus 2 to 5 for delivery. Two plants, West Chicago and Guangzhou.
Send the outer frame dimensions, the depth including hardware and the glazing type with your quote request and we will draw the internal size around the protection rather than around the frame alone. The full measuring routine, including the three box shapes that suit frames, is on how to size a picture frame box.
