Keep in mind that a wrong sized cooler can't help you maximize its function, even it can lead to waste. Thus, let's think about this thing:
Do you need to buy the best cooler for a single person, a couple, or a family of 4-5 people?
After answering, take a look at the following considerations:
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Internal space
When it comes to this aspect, consider 2 following elements:
- How much do you need to store in your cooler?
- And how long will you keep your contents in the cooler?
Don't forget to account for ice that takes a lot of space inside. For the maximum performance, keep in mind a 2:1 ratio of ice to consumables.
Thus, you must fill at least half of the cooler with ice, and only a half to a third of the model is for your food and drink.

Ice retention
Now, let's answer the following question:
How long do you need to keep ice in your cooler?
If you want to keep it cold for a long time, you shouldn't invest in a mini or personal cooler. It's too small for them to keep ice for a long day because there is not enough space to store a lot of ice.
In general, the more ice you store in your cooler, the longer your ice lasts.
In case you need to keep your ice more than 3 days, purchase a medium-sized cooler. For 5-7 days, I recommend you use a big cooler.
Portability
Small coolers are an excellent solution since it's effortless to transport these compact and lightweight models. A large cooler is not only hard to carry but also challenging to fit in your car.
If you want great portability, you need to make a trade-off with other features. You can't have all the outstanding features in only one product.
External space
Some Top Rated Camping Coolers

Weight
Typically, the larger your cooler is, the heavier it is. After you have done filling the unit with food and drink, the total weight is more. A too heavy cooler might make you painful.

Features
Though features have less impact on the size, it still influences your decision. High-performance coolers with too many features might restrict your cooler size. Some popular features of coolers include wheeled coolers and roto-molded cooler.
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To choose the best cooler size, you have to consider all elements, including internal space, ice retention, portability, external space, weight, and features. And remember that you can’t have all the great things in only one product. For example, you need to sacrifice portability to have more room for storing more food and drink for your long trip. If you know other things to add to this list, please leave a comment below.