It depends on how many days you'll be away. For trips of 1 to 5 days, a 55 cm cabin case (35-45 litres) is usually enough and lets you skip checking a bag in. For trips of 5 to 10 days, a medium case of 65-69 cm (60-80 litres) gives you more room, though you'll usually need to check it in. For more than 10 days, a large case of 75-82 cm (90-130 litres) is the option with the most capacity.
The most common mistake is buying one too big from the start: an empty large suitcase weighs more, costs more to check in, and is more awkward to handle day to day.
You'll find the full breakdown, with litres, empty weight and recommended models by size, in our complete guide to choosing your suitcase size.
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