What size cooler do I need? Quarts lie; here's the arithmetic

Quarts lie

The YETI Tundra 45 is 35.0 quarts by OutdoorGearLab's measurement; YETI itself rates it at 28 cans “with a 2-to-1 ice-to-can ratio.” The RTIC 45 is rated by RTIC at 60 cans without a ratio and measured 43.0 quarts. The Pelican 50QT is 52 quarts and rated 38 cans. The Engel 65 is 58 quarts and rated 70 cans at 2:1. Two things follow. First, the model number is a size class, not a volume; compare interior dimensions or measured quarts, both of which are on every product card on this site. Second, can counts mean nothing without a stated ice ratio, and only YETI and Engel state one.

The 2:1 rule

If what you are sizing is drinks rather than food, the same ratio is easier to apply in cans: how many cans fit in a cooler collects every maker's published can count for the coolers on this site and halves each one for a realistic ice load.

The corollary is that empty space is the enemy. A 65 packed one-third full with ice and food holds ice worse than a 45 packed to the lid, because the air inside a half-empty box is warmed every time the lid opens and has to be re-cooled by the ice. When in doubt, buy the smaller cooler and fill it, or fill the gap with frozen water bottles. How to keep ice longer ranks packing tricks by the hours they are worth.

Size by trip

Measured quarts are OutdoorGearLab's; rated quarts are the makers'. Usable space assumes a 2:1 ice-to-food load.

Interior length

For food, especially a fish or a week of flat-packed meals, the spec that matters is interior length, and the makers do publish it. RTIC 65: 26 in. Engel 65: 23.5 in. Tundra 65: 23.1 in. RTIC 45: 18.9 in. Tundra 45: 18.4 in. Engel 50: 18 in. Roadie 24: 10.9 in. For drinks, it is interior height: a 2-liter bottle needs about 13 in, which the Engel 50 (13.25), Pelican 50QT (13.7) and Roadie 24 (13.25) have and the RTIC 65 (12) and Tundra 45 (10.6) do not. Best coolers for fishing sorts by length; best coolers for camping by nights.

One pick per size

If the band is right and the brand is the question, the best hard coolers ranks every size on the full rubric, and the warranty comparison has the term for each.

If the answer you land on is 16 to 20 quarts, best small coolers ranks that size class on measured ice days, interior height and warranty term — and explains why a small cooler loses ice faster than anything bigger.

And once you know the quarts, the other half of the question is inches. Cooler dimensions and sizes lists the published exterior and interior measurements for fourteen coolers from 16 to 120 quarts, and computes how much of each one's length disappears into its own walls — five to twelve inches on a rotomold, under four on a thin-walled box. That is the number that decides whether the cooler fits the truck bed.