How to pack a cooler: the layer order, the ratio, and the one thing you should not drain

Before you pack anything

Two steps happen before the first item goes in, and skipping either costs you more ice than any packing order can win back.

Chill the cooler. A 45-quart rotomolded cooler is roughly 30 lb of plastic and foam sitting at room temperature, and your first several pounds of ice go into cooling that, not your food. How to pre-chill a cooler is the method and the timings.

Chill the contents. A cooler is an insulator, not a refrigerator — it has no way to remove heat from a warm six-pack except by melting your ice. Everything that goes in should come out of a fridge or a freezer. Room temperature cans are the single most common reason a cooler that measured four days in a lab lasts a day and a half on a trip.

The ratio the makers publish

Use that to set expectations before you shop as well as before you pack: a “60-can” cooler is a 28-can cooler once there is ice in it. What size cooler do I need does this sum for every size class, and how many ice packs do I need does it for reusable packs instead of bagged ice.

The layer order

Cold falls. That is the whole principle — chilled air is denser than warm air, so cold mass low in the cooler keeps working on everything above it, and cold mass on top does far less. Load in this order.

1. Cold mass on the floor. Block ice, frozen jugs or hard packs, laid flat across the bottom. This is the layer doing the long work, and it is the reason block ice earns its place — a block has less surface area per pound than cubes, so it melts more slowly. Block ice vs cubed ice is the honest version of that trade.

2. Frozen food next. Frozen meat is extra cold mass you were carrying anyway. Vacuum-sealed or double-bagged, directly on the ice layer.

3. Fridge-cold food above it. Anything that must stay below 40°F but must not freeze. Hard containers, not bags — packaging that holds its shape also holds its contents out of the meltwater.

4. Cubed ice into every void. This is the step people skip. Air is the enemy; pour loose ice into the gaps between packages until nothing shifts when you tilt the cooler. A cooler packed to the brim holds ice dramatically longer than the same cooler half full.

5. Drinks and anything you reach for, last and on top. If it is in the top layer you can get it out without excavating, which means the lid is open for five seconds instead of thirty.

6. A towel or a dry bag across the top. The headspace above the contents is the warmest air in the cooler; filling it with something dry and insulating is free.

One structural caveat: this layering only works if the cooler's interior is deep enough for layers. Published interior heights vary more than quart ratings suggest — the YETI Tundra 65 is 11.1 inches tall inside and the Tundra 45 is 10.6, while the Engel 50 and the YETI Roadie 24 are both over 13 inches and will stand bottles upright. Check the number before you plan the stack.

Why drinks belong in a second cooler

Every time the lid opens, the cold air falls out and warm air replaces it. On a normal day the drinks cooler is opened twenty or thirty times and the food cooler needs to be opened three. Putting both in one box means the food is paying for every beer.

So the cheapest upgrade to a cooler system is a second, smaller cooler for drinks — ideally one you do not care about, kept in the shade, re-iced freely. Best small coolers and best soft coolers cover that job, and best coolers for camping sorts coolers by how many nights you are out.

Do not drain the meltwater

Cold water is cold mass. Ice water sitting at 32°F is doing useful work, and the air that replaces it when you pull the plug is not. Drain it when you need the volume back for food, when it is getting into packaging, or when the cooler has had raw meat in it — not on a schedule.

The exception is any cooler carrying game or fish, where the water goes bad and the smell stays. That is a drain-often case, and a cooler with a plug that drains partially open — RTIC describes exactly that, over a channelled and recessed floor — is worth paying for. See best coolers for hunting and how to clean a cooler.