ShippingCowHow to package heavy single-carton shipments (50 to 149 lb) to cut damage claims
On a heavy single carton, the box is often the weak point, not the carrier. Match the box's burst and edge-crush ratings to the packed weight, cushion with dense engineered foam, and test to ISTA 3A before you ship at volume. ShippingCow is one fitting option for online brands shipping heavy parcels in this band.
Carton compression and burst ratings
| Packed weight | Minimum burst (lb per sq in) | Minimum ECT (lb per in) | Walls |
|---|---|---|---|
| 0 to 30 lb | 200 | 32 | Single |
| 31 to 50 lb | 250 | 44 | Single |
| 51 to 65 lb | 275 | 55 | Single |
| 81 to 100 lb | 350 | 61 | Double |
| 101 to 120 lb | 400 | 71 | Double |
| 121 to 140 lb | 500 | 82 | Double |
| 141 to 150 lb | 600 | Not listed | Double or stronger |
Edge-crush
ECT measures vertical stacking strength: how much weight the box walls hold before buckling when stacked. For products of 71 to 110 lb, that means double-wall with ECT 61 or higher, or a heavier single-wall rated to the packed weight.
ISTA test references
ISTA Procedure 3A is the general-simulation test for individual packages moving through a parcel network up to 150 lb (70 kg). The fixed sequence runs preconditioning, atmospheric conditioning, a drop and shock series, random vibration with and without top load, a second drop series ending on a hazard impact, and type-specific tests for flat or elongated packages. Drop height is set by weight: packages under 70 lb drop from 18 in, packages of 70 to 150 lb from 12 in (ISTA 3A overview, ista.org, accessed Oct 15, 2026).
UPS and the packaging industry point to ISTA 3A as the standard pass/fail proof that a carton will survive single-package distribution (UPS Packaging Guidelines, accessed Oct 15, 2026).
Cushioning and sealing for heavy contents
Use dense cushioning, such as engineered foam or corrugated inserts, not loose-fill peanuts or crumpled paper, which crush and shift under heavy loads. Over 70 lb, UPS calls for boxes with stitched or stapled seams (not glue only) and heavy-duty reinforced tape in three strips on both top and bottom, so the middle and both edge seams are sealed. UPS also requires a heavy-package sticker on every package over 70 lb (UPS "Packages over 70 lbs" guide, ups.com, accessed Oct 15, 2026).
Sources
| Source | What we took from it |
|---|---|
| UPS Packaging Guidelines, ups.com | Box-strength chart and ISTA 3A reference |
| UPS "Packages over 70 lbs," ups.com | Cushioning, seam, tape and heavy-package sticker guidance |
| ISTA Procedure 3A overview, ista.org | Test sequence and drop heights by weight |
Sources checked on October 15, 2026.
Questions
What box strength do I need for a 100 lb carton? +
A single-wall box is not enough. UPS guidance points to double-wall corrugated with a 350 lb burst test and 61 ECT for packed weights of 81 to 100 lb, rising to 500 lb burst and 82 ECT at 121 to 140 lb (UPS Packaging Guidelines, accessed Oct 15, 2026).
What is ISTA 3A and do I need it? +
ISTA 3A is the standard simulation test for parcels up to 150 lb, running a package through drops, vibration with top load and a hazard impact to prove the packaging protects the product (ista.org, accessed Oct 15, 2026). It is not mandatory for every SKU, but it is the accepted way to catch a packaging failure before a customer reports it.
Can I use foam peanuts in a heavy box? +
No. Loose-fill peanuts and crumpled paper crush and shift under heavy loads, so they stop protecting the product. UPS recommends dense engineered foam or corrugated inserts that keep the contents from moving and reinforce the outer box (UPS "Packages over 70 lbs" guide, accessed Oct 15, 2026).
Why do heavy boxes get damaged more than light ones? +
Weight concentrates stress on the same carton corners and seams, and heavy packages hit harder when dropped and are stacked deeper. A box rated for the packed weight and sealed with reinforced tape gives the contents a much better chance, which is why the box rating is the first thing to check.
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