For overnight shipping, plan on 5 to 10 pounds of dry ice for a standard insulated container up to 15 quarts. The exact amount depends on your container’s insulation quality, the size of the package, and how cold your contents need to stay. A well-insulated styrofoam shipper with a tight fit needs closer to 5 pounds, while a thinner or larger container may need the full 10.
Why the Range Is So Wide
Dry ice sublimates (turns directly from solid into gas) at a rate of roughly 10 pounds per 24 hours in a standard insulated container. That rate isn’t fixed. It changes based on several factors you can control:
- Insulation thickness. A 1.5-inch-wall styrofoam cooler loses dry ice much slower than a thin molded liner inside a cardboard box.
- Dead air space. The more tightly packed the container, the slower the sublimation. Fill empty gaps with crumpled newspaper, foam peanuts, or additional insulation.
- Ambient temperature. Shipping in July across the southern U.S. burns through dry ice faster than a December shipment in the Midwest. Summer shipments should lean toward the higher end of the range.
- Pre-chilled contents. If your items are already frozen solid before packing, the dry ice works less to maintain temperature. Room-temperature contents will eat through your supply quickly.
Scaling Up for Larger Packages
The 5-to-10-pound guideline applies to containers up to about 15 quarts, roughly the size of a small cooler. For larger shipments, multiply proportionally. A 30-quart container shipping overnight would need 10 to 20 pounds. If your transit window stretches to two days (common with “overnight” shipments that actually spend 30 to 36 hours in transit, including pickup and last-mile delivery), double the amount for a single day.
It’s better to overestimate slightly than to have your dry ice fully sublimate before delivery. A package that arrives with a small amount of dry ice remaining kept your contents at the right temperature the entire way. A package that ran out four hours early may not have.
Where to Place Dry Ice in the Box
Dry ice should go on top of your frozen items. Cold air sinks, so placing dry ice above the contents creates a blanket of extremely cold air that settles down through the package. Placing it only on the bottom lets the cold air pool beneath your product while warmer air sits on top.
Wrap the dry ice in a layer of newspaper or a small plastic bag (not sealed) before placing it in the container. This adds a slight insulation buffer that slows sublimation without blocking the cooling effect. Then fill any remaining airspace with packing material to minimize the volume of air the dry ice needs to keep cold.
Container Choice Matters
Styrofoam is the standard for dry ice shipments, and not just because it insulates well. Styrofoam is not airtight, which is critical. As dry ice sublimates, it produces carbon dioxide gas that expands significantly. Any sealed, airtight container can pressurize and violently rupture. Never use a sealed metal, plastic, or glass container unless it’s specifically rated for dry ice use.
Your outer cardboard box should not be taped completely airtight either. The gas needs a path to escape. Standard shipping boxes with normal taping are fine since cardboard is porous enough to vent slowly. Just avoid wrapping the entire outer box in shrink wrap or sealing every seam with heavy tape.
Carrier Rules and Labeling
Every major carrier treats dry ice as a Class 9 miscellaneous hazardous material, and each has its own rules.
UPS requires a Class 9 hazard label, a blue UPS dry ice label, and the marking “UN1845” on the outer box along with the net weight of dry ice in kilograms. If your package contains more than 2.5 kilograms (about 5.5 pounds) of dry ice, UPS requires a separate hazardous materials agreement. Since most overnight shipments need at least 5 pounds, you’ll likely need that agreement in place before shipping.
FedEx follows similar IATA standards: the outer package must display “UN1845,” the words “Dry ice” or “Carbon dioxide, solid,” the net weight in kilograms, a Class 9 label, and the full name and address of both shipper and recipient.
USPS is more restrictive. For air transportation, each mailpiece is limited to 5 pounds of dry ice. Surface shipments can exceed 5 pounds, but packages prepared for surface must never be routed via air under any circumstances. Since overnight delivery through USPS typically requires air transport, the 5-pound cap is a real constraint that may not be enough for larger packages.
Safe Handling While Packing
Dry ice sits at negative 109°F. Direct skin contact causes frostbite in seconds. Always wear insulated gloves and safety goggles when handling it. Standard kitchen gloves or thin latex gloves are not sufficient. Use gloves designed for extreme cold, like leather work gloves or cryogenic gloves.
Pack your shipments in a well-ventilated area. The carbon dioxide gas that dry ice releases displaces oxygen, and in a small or enclosed room, concentrations can build up enough to cause dizziness, headache, or difficulty breathing. A garage with the door open or a room with good airflow is ideal. Don’t pack dry ice shipments in a walk-in closet or a car with the windows up.
Quick Reference by Scenario
- Small box, overnight (under 15 quarts): 5 to 10 lbs
- Medium box, overnight (15 to 30 quarts): 10 to 20 lbs
- Small box, two-day shipping: 10 to 20 lbs
- Summer shipping or poor insulation: Add 25 to 50 percent more
- USPS air shipments: Maximum 5 lbs per package, which limits you to small, well-insulated containers
Buy your dry ice as close to packing time as possible. It starts sublimating the moment you purchase it, and storing it in your home freezer won’t help since household freezers are far warmer than dry ice temperature. Every hour between purchase and shipment costs you usable weight.