Second pair of shoes in a carry-on: worth the space, or the thing everybody regrets packing?

I carried a second pair on every trip for years and then counted the wears, which I recommend doing before this argument rather than during it.

On a two week trip the second pair got worn on about one and a half days, and one of those was because I wanted to, not because I needed to. That is a third of my bag for a day and a half.

But the counting also showed something I did not expect: the value was almost entirely in the days it rained, and those days were not optional or predictable. So the honest framing is not "is a second pair worth the space", it is "how likely is it that my only pair is unusable for a day".

Which gives you a rule rather than a preference:

• Dry season, cities, paved: no second pair. Genuinely.
• Anything where the primary pair can get soaked and take more than a night to dry: yes, and this is the whole case.

The part that decides it is drying time, not comfort. A pair of leather boots that takes two days to dry is a much stronger argument for a spare than a mesh trainer that is fine by morning. Work out how long your main pair takes to dry before you decide anything else.

The case nobody mentions: if the trail days are early in the trip, a second pair is insurance against the walking shoes being wrong. I found out on day two that a new pair rubbed, and having anything else meant the remaining twelve days were fine rather than ruined.

Break them in before you go and this argument mostly disappears.

A third of the bag is the number that should decide it. That is not a shoe question, that is a bag size question.

Agreeing with the drying-time point and adding the trick that let me drop the second pair entirely.

Wet shoes are mostly a problem because the inside stays wet. Stuffing them tightly with newspaper or any dry absorbent paper, changed once after an hour, dries them enormously faster than air alone: the paper is doing the wicking that the air cannot do inside a shoe. It is the difference between wearable by morning and wearable the day after.

If you carry a second pair, the two failure modes I would warn about:

The useless-but-light option. Thin flip-flops or packable slippers weigh nothing and cannot actually replace your main pair for a day of walking, so when it matters you are still in wet shoes. They are a shower and hostel-floor item, which is a real but different job.

The identical-purpose option. Two pairs of the same kind of shoe is a third of your bag spent on redundancy. If you take two, they should cover different situations: one that can get wet and dry fast, one that cannot.

Mine ended up as a light trail shoe worn on the plane and a pair of thin sandals that pack flat. The sandals are not a walking shoe and I do not pretend they are.

One reframe that helped me: the shoes are not competing with your other clothes, they are competing with the trip you are actually having.

You said a couple of days of trails inside two weeks of cities. Two days out of fourteen is not a trail trip with city stops, it is a city trip with two exceptions - and paying a third of your bag for two days is a bad rate unless those two days genuinely need a different shoe.

Worth asking honestly whether they do. A decent trail shoe is fine in a city and looks unremarkable almost everywhere now. The reverse is much less true, which is why "wear the bulkiest pair" is the standard advice - one shoe that covers both ends is the version of this that costs zero.

If the two trail days involve something a trail shoe is genuinely required for, that is a real constraint and you carry the second pair without guilt. But that is a small number of trips, and most people packing a spare are hedging against a version of the trip they are not going to have.