Mirrors fail in transit in two specific ways: a flat impact that cracks the glass, and an edge or corner impact that chips it and starts a crack later. Sizing is how you prevent both, because protection is mostly a question of how much space there is between the glass and the outside of the box.
Measure the piece, not the glass
Take three measurements from the finished product as it leaves your bench: height and width over the frame at its outermost edge, and thickness at the thickest point. That thickest point is usually the hanging hardware on the back, not the frame itself. A D ring, a sawtooth hanger or a wire bundle can add a surprising amount, and it is a point load pressing directly on whatever is behind it.
Add the cushioning before you add clearance
The usual carrier guidance for fragile goods is at least 2 in of cushioning between the item and the wall of the box on every face. Applied properly that means:
- Internal height = frame height + about 4 in (2 in top and 2 in bottom).
- Internal width = frame width + about 4 in.
- Internal depth = frame thickness including hardware + about 4 in, or less if you use a suspension or retention pack that holds the piece away from both faces.
A suspension insert, where the mirror is held between two membranes or two corrugated pads and never touches the outer wall, is the most material efficient way to hit that protection level. It is also the construction that survives a flat drop onto a corner, which is the drop that breaks mirrors.
Construction choices
| Construction | Best for | Sizing implication |
|---|---|---|
| Single piece double wall carton | Small and mid size framed mirrors | One internal size per product |
| Telescoping two piece | Tall pieces and mixed ranges | One base covers a range of heights by adjusting the lid overlap |
| Corner protectors plus a slim carton | Heavier framed pieces | Protectors add their own thickness to the internal plan size |
| Inner sleeve plus outer shipper | Retail presentation that also ships | Two internal sizes, the outer built to the outside of the inner |
Board direction matters too. Corrugated is far stiffer along the flutes than across them, so for a tall carton the flutes should run vertically, which is also what carries the stack load if these travel on a pallet.
Label the outside honestly
Fragile markings help but they do not change how a parcel is sorted. Treat the print on the box as instructions for the person unpacking it, not as protection. An arrow showing which way is up and a short line telling the customer to open the box flat on the floor prevents more breakages than a large fragile stamp.
Ordering
The minimum is 100 boxes, with pricing from about $0.48 per unit at bulk volumes confirmed on a written quote. The die, the plates, design support, US shipping and a digital proof are included, so a carton and insert cut for your exact frame costs no more to tool than a near standard box. Turnaround is quoted per job 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.
Send the frame dimensions, the hardware height and the weight of the piece to the quote form and we will come back with a carton and an insert option. Related: what size mirror box do I need and custom glassware boxes.
