Running out of ice on day two of a camping trip means warm drinks and, worse, food that is no longer safe. Buying too much wastes money and space. This calculator sizes the ice for your cooler and your trip.
The 2:1 rule
The most common advice is to fill a cooler with about two parts ice to one part food and drinks by volume. Ice is what keeps the cooler cold; the more of it, the longer everything stays below 40 °F. A 1:1 mix works for a day trip, and a cooler with less ice than contents will not hold cold for long.
A 48-quart cooler at 2:1 holds 32 quarts of ice. Ice weighs about 1.9 lb per quart of cooler space, so that is about 61 lb, or 7 bags of 10 lb, leaving 16 quarts for food and drinks.
Topping up on longer trips
Even a good cooler loses ice every day. How fast depends on the cooler, the weather, how often you open it and whether it sits in the sun. The calculator assumes a share of the ice melts each day (25% by default) and that you replace it:
total ice = initial ice × (1 + daily melt × (days − 1))
For 3 days at 25% a day: 61 × 1.5 = 92 lb, about 10 bags.
Rotomolded coolers with thick walls may lose only 10 to 15% a day in the shade; a thin cooler in a hot car can lose 50% or more.
Tips to make ice last
- Pre-chill the cooler the night before with a bag of sacrificial ice or frozen jugs.
- Chill or freeze the contents before packing. Frozen water bottles and frozen meals act as extra ice.
- Use block ice at the bottom: it melts more slowly than cubes. Add cubes on top to fill the gaps.
- Keep it in the shade and cover it with a blanket or towel.
- Use two coolers: one for drinks that is opened often, one for food that stays closed.
- Do not drain cold meltwater right away; it still keeps things cold. Drain it before adding new ice, and keep food in sealed bags or containers.
Food safety
Perishable food must stay at or below 40 °F (4 °C). Keep raw meat sealed and at the bottom, below ready-to-eat foods. When the ice is gone and food has been warm for more than two hours, throw it out.