Burst strength is a measurement of how much pressure a piece of corrugated board can take before it tears open. It is measured with the Mullen test, which pushes a rubber diaphragm against a clamped sample until the board ruptures, and the result is given in pounds per square inch. That is what people mean when they say a box is 200 pound test.
What burst strength actually tells you
It tells you how well the board resists a concentrated force pushing through it: a corner of another pallet, a forklift tine, a dropped item inside, a strap pulled too tight. It is a rupture measurement, so it speaks to abuse in handling rather than to load over time.
What it does not tell you is how many boxes you can stack. A box can have excellent burst resistance and still fail in a warehouse column, because standing up under a static load is a different physical problem.
Burst against edge crush
| Burst strength (Mullen) | Edge crush (ECT) | |
|---|---|---|
| What is measured | Pressure to rupture the board | Force to crush the board on edge |
| Units | Pounds per square inch | Pounds per inch of width |
| Answers | Will it survive rough handling and puncture? | Will it survive being stacked? |
| Favours | Heavier, denser liner papers | Stiffer board, often lighter in total weight |
| Best for | Dense or heavy single items, rough networks | Palletised goods, warehouse storage, columns |
Neither is better in the abstract. A box of heavy metal parts shipped as a single parcel is a burst problem. A pallet of light cartons stacked four high in a warehouse for three months is an edge crush problem.
The classification tables
Corrugated shippers have long been described against carrier classification tables that pair a burst figure with an ECT figure and a maximum gross weight. For single wall board, the conventional pairings are roughly:
| Burst test | Approximate ECT equivalent | Conventional maximum gross weight |
|---|---|---|
| 200 lb test | about 32 ECT | about 65 lb |
| 275 lb test | about 44 ECT | about 95 lb |
| 350 lb test | about 55 ECT | about 120 lb |
Treat these as industry reference figures for a conversation, not as a guarantee for your specific box. The figures that govern your shipment are the ones printed on the box maker's certificate for the board you actually buy.
What to do with this when you order
Do not ask for a strong box. Ask three concrete questions instead: what is the board grade, what maximum gross weight does the box maker's certificate state for it, and is it specified on burst or on edge crush. A supplier who answers those in writing is giving you something you can compare. A supplier who answers with adjectives is not.
Then match the answer to your actual failure mode. If your damage claims are punctures and torn corners, look at burst. If your claims are crushed boxes at the bottom of a pallet, look at edge crush and at how the pallet is built, because a box only carries load through its corners and any overhang throws that away.
How this affects your quote
Board grade is one of the main levers on the price of a corrugated box, alongside size and print coverage. Minimum order is 100 boxes, from about $0.48 per unit at bulk volumes, confirmed on your written quote. The die and plates, design support, US shipping and a digital proof before print are included.
Turnaround runs in three lanes: rush (expedited production with air freight), standard (air) and cost saver (sea), from about 7 business days plus 2 to 5 for delivery, with specialty imported items up to about 12 weeks. Rush adds about 7 to 25% depending on the job. We produce in West Chicago and Guangzhou. Plain shippers are on our corrugated boxes page.
Tell us what is inside, what it weighs and how it fails today, and request a quote. We will put the board grade and the gross weight limit in writing so you can compare it against anything else on your desk.
