What is the difference between mullen and ECT testing?

Corrugated boxes can be specified using different performance tests, and two of the most common terms buyers encounter are ECT and Mullen. Both describe characteristics of corrugated board, but they measure different types of strength.

ECT, or the Edge Crush Test, evaluates edgewise compression strength and is closely related to stacking and finished-box compression performance. The Mullen, or burst, test measures the pressure required to rupture the face of the corrugated board.

Neither test is universally “better.” The useful specification depends on what the package needs to withstand.

What Is the Mullen Burst Test?

The Mullen burst test, also called the bursting-strength test, measures the force required to rupture corrugated fiberboard using pressure applied through a rubber diaphragm.

Fibre Box Association technical definitions describe burst strength as relating indirectly to a box's ability to withstand external or internal forces. The applicable referee method is TAPPI T 810.

Burst strength is commonly reported in pounds per square inch, or psi. A specification such as 200# generally indicates a minimum burst-strength requirement of 200 psi.

It does not mean the finished box can safely hold 200 pounds of product.

What Is the Edge Crush Test?

ECT stands for Edge Crush Test. It measures the amount of force required to cause compressive failure of a corrugated-board specimen standing on its edge.

FBA identifies ECT as a primary factor in predicting the compression strength of a completed corrugated container.

ECT is reported as force per unit width, commonly pounds per inch. A rating such as 32 ECT therefore refers to edgewise compression strength, not to a 32-pound finished-box limit.

Why Was ECT Added?

Historically, carrier rules relied on Mullen burst strength and related board requirements to define minimum corrugated-box specifications.

In 1990, corrugated-industry trade associations sponsored proposals to add ECT as an alternate certification method. Those changes were approved in 1991 for motor-freight and rail carrier rules. FBA explains that ECT was introduced because burst properties do not provide a direct method for predicting stacking strength, while ECT is more closely related to box-compression performance.

That does not mean ECT replaced Mullen testing. Both methods continue to describe useful but different corrugated-board properties.

ECT vs. Mullen: What Does Each Test Measure?

Is One Test Better Than the Other?

Not universally.

If stacking strength is a primary design requirement, ECT is particularly useful because of its relationship to finished-box compression. FBA specifically describes ECT as the more appropriate measure when stacking strength is a primary design criterion.

Burst testing evaluates a different failure mode and can remain relevant where resistance to rupture, puncture, or forces acting against the board surface are important.

The correct question is therefore not “Which test is stronger?” but “Which performance characteristic matters for this package?”

Are ECT and Mullen Ratings Equivalent?

No. They should not be treated as direct equivalents because they measure different properties using different test methods.

You may see certain ECT and burst specifications listed as alternate minimum certification options within carrier or packaging requirements. For example, 32 ECT and 200 psi burst are both common single-wall specifications.

That does not mean 32 ECT mathematically equals 200# Mullen.

FBA guidance specifically states that no correlation method is available for converting Mullen or burst properties into stacking strength.

Why Do 32 ECT and 200# Often Appear Together?

32 ECT and 200# burst are commonly discussed together because they are frequently encountered as minimum specifications for single-wall corrugated boxes.

Current corrugated specification examples show separate Box Maker's Certificates using either an ECT value or a bursting-test value. One example identifies a 32 ECT single-wall box, while another identifies a 200 psi burst single-wall box. The allowable size and gross-weight limits shown for those examples are not identical, reinforcing that the two certifications are alternatives rather than direct equivalents.

For a buyer-focused comparison of those two common specifications, see our guide to 32 ECT vs. 200# Corrugated Boxes.

ECT Is Not the Same as Box Compression Testing

Another important distinction is between the Edge Crush Test and a Box Compression Test, or BCT.

ECT evaluates corrugated board. BCT evaluates the compression strength of the completed box.

ECT is one important input used in predicting finished-container compression performance, but the finished box is also affected by dimensions, flute, box design, manufacturing, stacking pattern, humidity, storage time, and other factors.

FBA's ECT reference materials include formulas and performance data relating ECT to BCT specifically because the two values are connected but are not the same measurement.

Why the Finished Box Still Matters

Neither an ECT rating nor a Mullen rating tells you everything about how a finished package will perform.

Actual performance can be influenced by:

• Box dimensions.
• Single-wall, double-wall, or triple-wall construction.
• Flute profile.
• Box style.
• Product weight and weight distribution.
• Internal packaging.
• Sharp or irregular contents.
• Stacking height and pallet pattern.
• Humidity and moisture exposure.
• Storage duration.
• Handling and transportation conditions.

That is why board-test ratings should be used as part of a complete package specification rather than as standalone product-weight limits.

For a broader explanation, see How Much Weight Can a Corrugated Box Hold?

What Is a Box Maker's Certificate?

A Box Maker's Certificate, commonly called a BMC, can be printed on a corrugated shipping container to identify the manufacturer and certify that the box meets applicable construction requirements.

Depending on the certification method, a BMC may identify an Edge Crush Test value or a bursting-test value along with applicable size and gross-weight limits. Current carrier rules define both ECT and bursting-strength specifications within corrugated-box requirements.

The Bottom Line

ECT and Mullen measure different aspects of corrugated-board performance.

ECT measures edgewise compression and is especially useful when stacking and box-compression performance are important. The Mullen burst test measures the pressure required to rupture the board and evaluates a different type of resistance.

Neither rating is a universal finished-box weight limit, neither is automatically better, and the two should not be directly converted into one another.

The best corrugated specification considers the board test together with box dimensions, construction, contents, storage, palletization, and the complete distribution environment.

Need Help Choosing Corrugated Board Strength?

Browse corrugated packaging or Contact Packaging HERO if you need help evaluating ECT, burst strength, wall construction, dimensions, or other corrugated specifications for your application.

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