How much dry ice can I ship with FedEx?

FedEx lists a 200 kg maximum dry ice quantity per package. FedEx air shipments need UN1845 marking, the proper shipping name, net weight in kg, and a Class 9 hazard label (minimum 100mm diamond). For air shipments, the AWB must include the dry ice description.

Do I need a Class 9 label for ground shipments?

FedEx Ground dry ice is not regulated as hazardous material in the same way as air service, but FedEx still says to mark the package as dry ice. UPS says dry ice shipments to and from the U.S. 48 contiguous states are processed like standard UPS Ground. USPS surface mail needs a 'Surface Only' or 'Surface Mail Only' marking. Always verify current requirements with your carrier.

Can I ship dry ice internationally with USPS?

No. USPS does not accept international mail containing dry ice. For international dry ice shipments, you must use FedEx, UPS, or another carrier that supports international dangerous goods transport.

What is the UPS 2.5 kg threshold for dry ice?

For UPS domestic air shipments with non-medical contents, packages containing more than 2.5 kg of dry ice go through an acceptance audit path with additional verification requirements. Packages with 2.5 kg or less may follow a simplified 49 CFR handling path when properly marked with dry ice or carbon dioxide solid, the contents being cooled, and the dry ice amount.

Can USPS ship dry ice internationally?

No. USPS does not accept international mail containing dry ice, regardless of quantity.

How much dry ice can USPS air mail contain?

USPS air mail is limited to 5 lb, about 2.27 kg, of dry ice per mailpiece.

USPS dry ice shipping rules (UN1845)

USPS has the most restrictive dry ice shipping policies of the three major U.S. carriers. Dry ice (UN1845, Carbon dioxide, solid, Class 9) is accepted by USPS, but with significant limitations on weight, mode, and international eligibility. Understanding these rules is critical because violations can result in rejected shipments at the post office counter — or worse, shipments pulled from the mail stream in transit.

Here's what you need to know before shipping dry ice through USPS.

Can You Ship Dry Ice with USPS?

Yes, but with conditions. USPS accepts dry ice shipments domestically when the dry ice is used as a refrigerant for non-hazardous contents. However, USPS has three major restrictions that FedEx and UPS do not:

5-pound weight limit for air services — USPS caps dry ice at 5 lbs (approximately 2.27 kg) per mailpiece for air transport
International shipments are prohibited — USPS does not accept any international mail containing dry ice
Surface (ground) transport has different marking requirements — specifically, a "Surface Only" or "Surface Mail Only" marking

These restrictions make USPS a viable option for smaller domestic dry ice shipments but unsuitable for larger quantities, international routes, or situations where you need the flexibility of air transport with higher weight limits.

USPS Dry Ice Weight Limits

Air Transport: 5 lbs Maximum

For any USPS service that may travel by air — including Priority Mail, Priority Mail Express, and First-Class Mail on routes that are air-transported — the maximum amount of dry ice per mailpiece is 5 pounds (2.27 kg).

This is a hard limit. A package containing more than 5 lbs of dry ice cannot be sent via any USPS air service. If you need to ship larger quantities, you'll need to either split the shipment into multiple packages (each under 5 lbs) or use FedEx or UPS.

Ground Transport: No Specific Weight Limit Listed

USPS Retail Ground (formerly Parcel Post) and other surface-only services do not have the 5-pound dry ice cap, since the restriction is specifically tied to air transport. However, USPS still requires compliance with all marking and labeling requirements, and the standard USPS package weight limits apply.

If you ship dry ice via USPS Ground, you must include a "Surface Only" or "Surface Mail Only" marking on the outer package. This ensures the mailpiece is not inadvertently placed on an aircraft.

USPS International Dry Ice: Prohibited

USPS does not accept dry ice in any international mail class. This includes Priority Mail International, Priority Mail Express International, First-Class Mail International, and all other international products.

If you need to ship dry ice internationally from the U.S., your options are FedEx or UPS (both accept international dry ice shipments with appropriate documentation, though UPS may require a dangerous goods contract).

This prohibition applies regardless of the quantity of dry ice — even a small amount disqualifies the mailpiece from international USPS service.

USPS Dry Ice Labeling Requirements

Class 9 Hazard Label

For USPS air services, each package containing dry ice must display a Class 9 hazard label (the black-and-white striped diamond with "9" in the corner). The label should be at least 100mm x 100mm for air transport, matching the IATA standard.

For USPS surface/ground transport: The Class 9 label requirement differs. USPS ground-only shipments may not require the Class 9 diamond in the same way air shipments do, since ground transport falls under DOT regulations rather than IATA. However, the outer marking requirements (UN1845, proper shipping name, net weight) still apply.

Outer Package Markings

Every USPS dry ice package must be marked with:

"UN1845" — the UN identification number
"Dry Ice" or "Carbon dioxide, solid" — the proper shipping name
Net weight of dry ice in the package (in pounds or kilograms)

Surface Only Marking (Ground Shipments)

If you are shipping dry ice via USPS ground/surface transport, you must also mark the outer package with "Surface Only" or "Surface Mail Only." This is a USPS-specific requirement that prevents the mailpiece from being loaded onto an aircraft. Omitting this marking on a ground-only shipment risks having the package rerouted to air transport, where it may violate the 5-pound limit or be flagged in transit.

Packaging Requirements

USPS packaging standards for dry ice are consistent with general dangerous goods packaging principles:

Ventilation: The package must allow CO2 gas to escape. Never use an airtight container for dry ice — the pressure from sublimating CO2 can rupture the packaging.
Insulation: Use a polystyrene foam cooler or similar insulated container inside a sturdy corrugated outer box.
Contents separation: Items being cooled should not be in direct contact with dry ice. Use packing material or an additional insulation layer as a barrier.
Labeling placement: All markings and labels must be on the outer shipping container, clearly visible and legible.

USPS Dry Ice at the Post Office Counter

Shipping dry ice via USPS often involves a counter interaction at the post office. Here's what to expect:

Inform the postal clerk that your package contains dry ice (UN1845, Class 9)
The clerk may ask about the quantity (weight) and whether the contents are hazardous
Be clear that the dry ice is used as a refrigerant for non-dangerous goods
If shipping ground, confirm you want surface-only transport and that the package is marked accordingly
Some post offices have limited familiarity with dry ice shipment procedures — having your documentation pre-printed and organized will speed up the process significantly

A prepared counter script (what to say, what questions to expect, what documents to show) can make the difference between a smooth drop-off and a frustrated back-and-forth.

When to Use USPS vs. FedEx or UPS for Dry Ice

USPS makes sense for dry ice shipments when:

Domestic only (no international)
Quantity is under 5 lbs per package (for air)
Cost sensitivity is a priority (USPS rates are often lower for small packages)
You're comfortable with the surface-only option for larger quantities

Switch to FedEx or UPS when:

You need to ship more than 5 lbs of dry ice per package via air
The shipment is international
You need guaranteed air transit with higher weight allowances
You want a more established dangerous goods acceptance process

Common Reasons USPS Rejects Dry Ice Shipments

Exceeding the 5-lb air limit — the most common failure; your only option is to split packages or switch to ground
International destination — USPS flatly prohibits dry ice in international mail
Missing "Surface Only" marking on ground shipments — required to prevent air rerouting
No UN1845 or net weight marking — postal clerks are trained to check for these
Airtight packaging — safety violation; the container must vent
Clerk unfamiliarity — having printed documentation and a clear counter script reduces friction

Generate Your USPS Dry Ice Documentation Instantly

Dry Ice Wizard evaluates your USPS shipment against all carrier-specific rules and generates the required documentation automatically. It flags the 5-lb air limit, catches international prohibitions, and adds the "Surface Only" marking for ground shipments.

Enter your shipment details and get:

Instant compliance evaluation (green/yellow/red)
Clear explanation of any prohibitions (e.g., international is blocked)
Print-ready Class 9 labels at the correct size
Outer markings with your specific weight and contents
Acceptance checklist tailored to USPS
Counter script for the post office interaction

Check your USPS dry ice shipment now →

Important Notes

This guide is informational and not legal advice. Verify current requirements with USPS Publication 52, Section 349.32, Packaging Instruction 9A, and applicable DOT/IATA regulations.
Rules referenced here were last reviewed in June 2026.
This applies only to dry ice used as a refrigerant for non-dangerous goods. If your dry ice is packaging other hazardous materials, additional regulations apply.

Last updated: June 2026 | dryicecompliance.com