What size soft cooler do I need? Use the measured liters, not the can count

Halve the can count, then check the liters

Soft coolers are sold by cans and the number always assumes an empty bag. RTIC advertises 30 cans for its Ultra-Tough Soft Cooler and separately states it holds 18 lb of ice; YETI rates its hard Tundra 45 at 28 cans at a “2:1 ice-to-can ratio” against 60 cans with no ice for a comparable 45-quart box. The same arithmetic applies in fabric: a 30-can soft cooler carries roughly 15 cans once there is enough ice in it to matter.

The second problem is that can counts are not comparable between brands, because a can count depends on how you stack them. OutdoorGearLab measured the usable volume of each bag in liters, and the results cut across the labels: the “30 can” RTIC measured 18.0 L, the “30 can” Titan Deep Freeze measured 19.4 L, YETI's “Flip 18” measured 16.4 L and held 30 cans, and the Engel HD30 — sold as 32 quarts — measured 41.8 L and 63 cans. Liters are the number to shop on.

Measured liters, side by side

Size against measured ice days

Bigger bags hold ice longer, for the same reason bigger hard coolers do: less wall per liter of contents. The measured results show the trend and also show how loose it is.

At 10.8 liters the YETI Hopper Flip 12 managed 1.6 days below 40°F. At 18.0 liters the RTIC 30 Can managed 1.8 days. At 19.4 liters the Titan Deep Freeze 30 managed 2.1 days. At 16.4 liters the Hopper Flip 18 managed 2.4 days. At 20.1 liters the Hopper M20 managed 3.6 days — the best result of the group. And at 41.8 liters, more than twice the M20's volume, the Engel HD30 managed 3.0 days.

Whatever size you land on, the honest expectation for a soft cooler is one to two days with the lid opening, not the three days the claims suggest. That is set out with the measurements in soft cooler ice retention: what to expect.

The real limit is your shoulder, not the bag

A soft cooler is carried, so its empty weight matters less than its loaded weight — and loaded weight is a function of liters, not of the bag. Water and ice run about 2 lb per liter, so a 20-liter bag packed with ice and drinks is somewhere around 40 lb hanging off one shoulder, and a 42-liter Engel packed the same way is a two-handed lift.

That is the point where the format changes rather than the size. Above about 25 liters of regular use, the honest options are a backpack cooler, which puts the load on both shoulders, or a hard cooler with a handle at each end:

Empty weights for reference, all from the makers or the lab: AO Canvas 24 at 2.8 lb, YETI Hopper Flip 12 at 3.6, RTIC 30 Can at 3.7, Titan Deep Freeze 30 at 3.6, Flip 18 at 4.4, Engel HD30 at 4.5 and Hopper M20 at 5.2. Every one of them is light empty; none of them is light full. Best backpack coolers covers the two-shoulder answer and hard cooler vs soft cooler covers the other one.

Which YETI or RTIC size

YETI. The Hopper Flip 12 (10.8 L measured, 1.6 days) is a lunch-and-two-drinks bag — take it only if you genuinely want something that small. The Flip 18 (16.4 L, 2.4 days) is the one most people should buy: nearly a day more ice than the 12 for about a pound more weight. The Hopper M20 (20.1 L, 3.6 days) is the best-measured soft cooler of this group and it is a backpack, which is how it gets away with the extra load. All three carry YETI's 3-year Hopper term.

RTIC. The 30 Can Ultra-Tough Soft Cooler measured 18.0 L and 1.8 days, with a waterproof zipper, up to 1.5 inches of foam and a 1-year term limited to the original retail purchaser. It is the cheapest Hopper-style bag here and the term is the trade. If you are choosing between the two brands directly, that is YETI Hopper vs RTIC Soft Pack.

And if the bag is mostly for a lunch break rather than a day out, drop a size class entirely — best lunch coolers is the 9 to 16 liter field, where a single hard ice pack is the whole cooling load.