Dry ice travels under UN1845 as a Class 9 hazardous material because it sublimates into carbon dioxide gas that can burst sealed boxes and displace breathable air. Carriers do accept it, each under its own weight limits and marking rules, which we checked against their sites on 2026-07-27. SMKlog's own checkout does not sell dry ice labels at all, and this page shows exactly what happened when we tried.
Every limit in the table names the carrier site it came from and the day we checked it.
No prices appear below because we do not sell this shipment type; what a dry ice shipper needs instead is the rulebook. These are the headline constraints from each carrier's own pages, condensed. Read the source before shipping, since dangerous goods rules shift without ceremony.
| Carrier | Headline limit | Key conditions | Source |
|---|---|---|---|
| USPS | 5 lb max by air | Package must vent gas; no international or APO/FPO/DPO destinations | pe.usps.com, Pub 52 |
| UPS | 2.5 kg on domestic air without hazmat processing | Ground in the 48 states not regulated; mark Dry Ice, UN1845 and weight in kg; Class 9 diamond optional under 49 CFR; AK, HI, PR move as air | ups.com |
| FedEx | 200 kg per package | Vented fiberboard, plastic or wood only, never airtight; mark contents, UN 1845 and kg; Class 9 label for air; ground movements still need marking and driver notice | fedex.com |
FedEx's guidance also suggests planning around 5 to 10 pounds of dry ice per 24 hours of transit, which is a useful sizing rule wherever you ship. The pattern across all three carriers is identical: ground is lenient, air is strict, and the box must never be able to hold pressure. Packing technique for the cooler itself is covered in our insulated box guide, and gel-pack alternatives in the cold food guide.
On 2026-07-27 we asked our own calculator to price frozen steaks packed with dry ice from Newark to Atlanta. It returned no rates and this refusal instead:
"SMKlog online labels are not available for perishable, live, biological, dry ice, frozen, animal, or plant material. Do not continue with self-service checkout for these contents."
That block is policy, not a glitch, and it matches our shipping restrictions page. Shippers who genuinely need a dry ice lane should work directly with a carrier's dangerous goods program, where trained acceptance and the right paperwork exist.
Sublimating dry ice expands enormously as gas. In a vented cooler that gas drifts out harmlessly; in a taped-airtight container it builds pressure until something gives. Every carrier prohibition on sealed drums and airtight packaging traces back to this one piece of physics.
Surface contact with dry ice injures skin in seconds, which is a handling fact as much as a shipping one. Whoever unpacks the box deserves a heads-up too; a note inside telling the recipient not to grab the remaining pellets bare-handed is a small courtesy that prevents a real injury.
For refrigerated rather than frozen targets, frozen gel sidesteps UN1845 entirely: no markings, no limits, no Class 9 anything. Plenty of shipments reach for dry ice out of habit when a chilled range would have satisfied the recipient just as well.
Yes, it is UN1845, a Class 9 miscellaneous hazardous material. The gas it releases displaces oxygen in closed spaces and pressurizes sealed containers, which is why every carrier requires packaging that vents and marking that names the contents.
It depends on carrier and mode. Per pe.usps.com, USPS allows up to 5 lb per mailpiece by air; per ups.com, UPS treats up to 2.5 kg on domestic air without full hazmat processing while ground in the lower 48 is not regulated; per fedex.com, FedEx caps a package at 200 kg. All checked 2026-07-27.
Our online checkout excludes dry ice along with perishable, frozen and biological contents, and the quote engine enforces that automatically. We tested it while writing this page and the engine declined the shipment, exactly as the shipping restrictions page says it should.
Carriers require the words Dry Ice or Carbon Dioxide Solid, the UN1845 designation and the net quantity in kilograms on the outer box, with a Class 9 label added for air movements. The specifics differ by carrier and mode, so the carrier's own dangerous goods pages are the source to follow.