How Much Weight Can a Corrugated Box Hold? Weight Limits by ECT and Mullen

Updated September 2, 202616 certified grades, 23 to 100 ECT1,969 stocked boxes

A corrugated box holds what its box maker's certificate says: 65 pounds gross for 32 ECT (200 lb test), 95 pounds for 44 ECT, 100 pounds for 48 ECT double wall and up to 340 pounds for triple wall. The table below lists every certified grade with its gross-weight and size limits, the stacking-load estimates for stocked sizes, and which grade to buy for a given packed weight.

Weight limits by grade: the box maker's certificate table

Every corrugated box sold for shipping carries a round or rectangular box maker's certificate on the bottom flap. It states the board grade two ways, as a Mullen burst value in pounds per square inch or as an edge crush value in pounds per inch, and it states the maximum gross weight the carrier classifications allow for that grade. That gross-weight number is the honest answer to how much weight a corrugated box can hold for parcel or LTL shipment. It comes from the Fibre Box Association and the carrier rules, not from the manufacturer's marketing, and it is the number a carrier can cite when it declines a damage claim on an overloaded box.

Limits printed on the box maker's certificate per the Fibre Box Association and carrier classification (UFC Rule 41 / NMFC Item 222). Gross weight is the carrier ceiling for the box as shipped; it is not a stacking figure.
Board Mullen burst ECT Max gross weight (box + contents) Max L + W + H Packrift stock
Single wall 125 lb/sq in 23 ECT 20 lb 40 in not stocked
Single wall 150 lb/sq in 26 ECT 35 lb 50 in not stocked
Single wall 175 lb/sq in 29 ECT 50 lb 60 in not stocked
Single wall 200 lb/sq in 32 ECT 65 lb 75 in 1,667 stocked sizes
Single wall 275 lb/sq in 44 ECT 95 lb 85 in 98 stocked sizes
Single wall 350 lb/sq in 55 ECT 120 lb 100 in not stocked
Double wall 200 lb/sq in 42 ECT 80 lb 85 in not stocked
Double wall 275 lb/sq in 48 ECT 100 lb 95 in 180 stocked sizes
Double wall 350 lb/sq in 51 ECT 120 lb 105 in 8 stocked sizes
Double wall 400 lb/sq in 61 ECT 140 lb 110 in not stocked
Double wall 500 lb/sq in 71 ECT 160 lb 115 in 5 stocked sizes
Double wall 600 lb/sq in 82 ECT 180 lb 120 in not stocked
Triple wall 700 lb/sq in 67 ECT 240 lb 110 in not stocked
Triple wall 900 lb/sq in 80 ECT 270 lb 115 in not stocked
Triple wall 1100 lb/sq in 90 ECT 300 lb 120 in 11 stocked sizes
Triple wall 1300 lb/sq in 100 ECT 340 lb 125 in not stocked

Two things stand out in the table. First, the jump from 32 ECT to 44 ECT buys 30 more pounds of allowance, and the jump to 48 ECT double wall buys another 5 pounds plus far more resistance to puncture and stacking collapse. Second, the combined length plus width plus height limit rises with the grade: a 32 ECT box is only certified to 75 inches of combined outside dimensions, which is why a 30 x 24 x 24 box (78 in) is normally made in 44 ECT or double wall. The ECT to Mullen conversion chart explains why the two scales do not line up one to one.

Stacking strength is a different number

Gross weight limits describe one box in transit. Warehouse stacking asks a different question: how much weight can the bottom box carry when a column of boxes sits on it for weeks. That is box compression strength, estimated from ECT with the McKee formula, and it depends on the box perimeter and the board caliper as much as on the grade. A large box has a longer perimeter of vertical wall and therefore a higher compression value than a small box of the same grade, which surprises people who assume small boxes are stronger.

BCT estimated with the McKee formula (5.87 x ECT x square root of caliper x perimeter) using typical calipers of 0.16 in single wall, 0.28 in double wall. The BCT / 4 planning estimate leaves margin for humidity, storage time, pallet overhang and misaligned columns. Estimates only; test your own pack.
Stocked box Grade Perimeter Estimated box compression (BCT) Planning stack-load estimate (BCT / 4) Rule of thumb
12 x 12 x 12 32 ECT 48 in 521 lb 130 lb 130 lb per ft of stack
12 x 12 x 12 44 ECT 48 in 716 lb 179 lb 179 lb per ft of stack
12 x 12 x 12 48 ECT 48 in 1,033 lb 258 lb 258 lb per ft of stack
12 x 12 x 12 71 ECT 48 in 1,528 lb 382 lb 382 lb per ft of stack
12 x 12 x 12 90 ECT 48 in 2,714 lb 679 lb 679 lb per ft of stack
16 x 16 x 16 32 ECT 64 in 601 lb 150 lb 113 lb per ft of stack
16 x 16 x 16 44 ECT 64 in 826 lb 207 lb 155 lb per ft of stack
16 x 16 x 16 48 ECT 64 in 1,193 lb 298 lb 224 lb per ft of stack
16 x 16 x 16 71 ECT 64 in 1,764 lb 441 lb 331 lb per ft of stack
16 x 16 x 16 90 ECT 64 in 3,134 lb 784 lb 588 lb per ft of stack
18 x 18 x 18 32 ECT 72 in 638 lb 159 lb 106 lb per ft of stack
18 x 18 x 18 44 ECT 72 in 877 lb 219 lb 146 lb per ft of stack
18 x 18 x 18 48 ECT 72 in 1,265 lb 316 lb 211 lb per ft of stack
18 x 18 x 18 71 ECT 72 in 1,871 lb 468 lb 312 lb per ft of stack
18 x 18 x 18 90 ECT 72 in 3,325 lb 831 lb 554 lb per ft of stack
24 x 24 x 24 32 ECT 96 in 736 lb 184 lb 92 lb per ft of stack
24 x 24 x 24 44 ECT 96 in 1,012 lb 253 lb 127 lb per ft of stack
24 x 24 x 24 48 ECT 96 in 1,461 lb 365 lb 183 lb per ft of stack
24 x 24 x 24 90 ECT 96 in 3,839 lb 960 lb 480 lb per ft of stack
12 x 10 x 8 32 ECT 44 in 498 lb 125 lb 187 lb per ft of stack
12 x 10 x 8 44 ECT 44 in 685 lb 171 lb 257 lb per ft of stack
20 x 20 x 20 32 ECT 80 in 672 lb 168 lb 101 lb per ft of stack
20 x 20 x 20 44 ECT 80 in 924 lb 231 lb 139 lb per ft of stack
20 x 20 x 20 48 ECT 80 in 1,334 lb 333 lb 200 lb per ft of stack
20 x 20 x 20 71 ECT 80 in 1,973 lb 493 lb 296 lb per ft of stack
16 x 12 x 8 32 ECT 56 in 562 lb 141 lb 211 lb per ft of stack
16 x 12 x 8 44 ECT 56 in 773 lb 193 lb 290 lb per ft of stack
16 x 12 x 8 48 ECT 56 in 1,116 lb 279 lb 418 lb per ft of stack
24 x 18 x 12 32 ECT 84 in 689 lb 172 lb 172 lb per ft of stack
24 x 18 x 12 44 ECT 84 in 947 lb 237 lb 237 lb per ft of stack
24 x 18 x 12 48 ECT 84 in 1,366 lb 342 lb 342 lb per ft of stack
14 x 14 x 14 32 ECT 56 in 562 lb 141 lb 120 lb per ft of stack
14 x 14 x 14 44 ECT 56 in 773 lb 193 lb 166 lb per ft of stack
14 x 14 x 14 48 ECT 56 in 1,116 lb 279 lb 239 lb per ft of stack
14 x 14 x 14 71 ECT 56 in 1,650 lb 413 lb 354 lb per ft of stack
14 x 14 x 14 90 ECT 56 in 2,932 lb 733 lb 628 lb per ft of stack
10 x 10 x 10 32 ECT 40 in 475 lb 119 lb 143 lb per ft of stack
10 x 10 x 10 44 ECT 40 in 653 lb 163 lb 196 lb per ft of stack
10 x 10 x 10 48 ECT 40 in 943 lb 236 lb 283 lb per ft of stack

Use the BCT / 4 column as a planning estimate. Corrugated loses roughly half its dry compression strength at 85 to 90 percent relative humidity, loses more the longer it is stacked, and loses more again when boxes are misaligned or overhang the pallet. A divisor of four provides a planning margin; humid storage, mixed loads or racking without pallets may require a larger margin. Test the actual pack before setting a stack height. The pallet count table pairs with this page when planning stack heights.

Which grade to buy

Grade Stocked products Typical use Example
32 ECT 1,667 Standard e-commerce and retail shipping, parcel carriers, loads to 65 lb 4x4x4 ECT-32 Kraft Cube Corrugated Shipping Boxes 25-Pack from $8.07
44 ECT 98 Heavier single-wall loads to 95 lb, taller pallet stacks, long boxes 6x6x6 ECT-44 Kraft Heavy-Duty Corrugated Shipping Boxes 25-Pack from $18.87
48 ECT 180 Double wall for 100 lb loads, fragile or dense goods, LTL freight 8x8x8 ECT-48 Kraft Double Wall Corrugated Boxes 15-Pack from $19.37
51 ECT 8 Double wall for 120 lb loads and 105 in combined size 30x17x17 ECT-51 Double Wall Corrugated Boxes 5-Pack from $40.06
71 ECT 5 Double wall for 160 lb loads, machinery and bulk parts 14x14x14 ECT-71 Heavy-Duty Double Wall Corrugated Shipping Boxes 15-Pack from $131.22
90 ECT 11 Triple wall for 300 lb loads, bulk bins, gaylords 14x14x14 ECT-90 Triple Wall Corrugated Boxes 5-Pack from $115.47

For many parcel shipments, 32 ECT is a practical starting point; confirm the box maker's certificate and the current carrier's service-specific packaging requirements. Its listed 65 pound gross allowance can guide selection, but packed weight, dimensions, contents and handling still matter. Move to 44 ECT when the packed weight passes about 50 pounds, when the box is long or tall, or when it will sit at the bottom of a pallet column. Move to double wall when the contents are dense, sharp or worth more than the box, and for anything shipped LTL, where forklift handling and stacking are the norm. The single wall vs double wall guide covers the board difference, and the flute types chart explains why the same ECT feels different on B, C and BC board.

Reading the certificate on your own box

  1. Find the stamp. It is printed on a bottom flap, usually near a corner.
  2. Read the test type. A burst-test certificate shows a value like 200 lbs per sq inch; an edge-crush certificate shows a value like 32 ECT. Boxes are certified by one test or the other, not both.
  3. Read the size limit. The stamp lists the maximum combined outside dimensions and the maximum gross weight for the grade.
  4. Compare with your packed weight. Weigh the packed box. If it is over the stamp's gross weight, check the carrier's current packaging and claims terms; step up a grade rather than adding tape.
  5. Check the flute. The stamp does not always name the flute; the flute chart shows how to tell B, C and BC apart by thickness.

What the limits do not cover

The gross weight limits assume a box in good condition, closed with tape across the center seam, filled so the contents cannot shift. A box with crushed corners, a wet bottom, or a 3 inch void above the contents will fail well under its rating. Dense contents concentrate weight on a small area of the bottom panel; a 60 pound case of bolts in a 32 ECT box is within the rating and still likely to punch through unless the bottom is padded. When in doubt, the cost of stepping from 32 to 44 ECT on a stocked size is usually 10 to 20 percent of the box price, and far less than one damaged shipment.

Shop 32 ECT shipping boxesShop double wall boxesBulk quote

Frequently asked questions

How much weight can a 32 ECT box hold?

Up to 65 pounds gross (box plus contents) under the box maker's certificate, with combined outside dimensions up to 75 inches. Stacking capacity is separate and depends on box size; for a 16 x 16 x 16 in 32 ECT box, the table's BCT / 4 planning estimate is about 150 pounds of top load under the stated assumptions.

How much weight can a 44 ECT box hold?

Up to 95 pounds gross, with combined dimensions up to 85 inches. It is the single-wall grade for loads between 50 and 95 pounds and for long or tall boxes.

How much weight can a double wall box hold?

80 to 180 pounds gross depending on grade: 42 ECT is rated 80 lb, 48 ECT 100 lb, 51 ECT 120 lb, 61 ECT 140 lb, 71 ECT 160 lb and 82 ECT 180 lb. Triple wall runs from 240 to 340 pounds.

Is 200 lb test the same as 32 ECT?

They are equivalent grades with the same 65 pound gross weight limit, but they are different tests. Burst (Mullen) measures resistance to puncture; ECT measures edge compression, which predicts stacking. See the ECT to Mullen conversion chart.

What happens if I ship a box over its weight limit?

A carrier may accept the shipment, but claim handling depends on the current carrier terms and the packaging used. Step up a grade instead.

Related references

Related references

Related references