Not every Greek escape begins in Santorini
Quiet Greek islands with airports, direct flights and an extra ferry
Quiet Greek islands are quiet for a reason, and the reason is almost always the connection. The greek islands with airports are one list and the ones worth an extra ferry are another; this page sorts them by how hard they are to reach, because that is what keeps them empty.
Why the connection decides which Greek islands stay quiet
An island's popularity tracks how easy it is to get to far more closely than it tracks how beautiful it is. Put an airport on a rock and it fills; leave it with one boat a day and it stays as it was. That is the whole mechanism, and it means the search for quiet greek islands is really a search through the timetable.
It also means the trade is explicit, not hidden. The least touristy greek islands cost a travel day at each end, and the ones that cost nothing extra to reach are busy. What follows splits them on exactly that line.
Quiet Greek islands with airports and direct flights to the gateway
These are the greek islands with airports of their own, reached by a flight rather than by a long crossing, usually a short hop from a gateway. They are the compromise: quieter than the famous islands, without a day at sea. Being greek islands with airports does not make them busy, because the flights that serve them are small and seasonal.
The gateways those hops leave from are Athens, Rhodes, Santorini. Direct flights from the UK reach the gateways, not the islands, so the second leg is the part to check before booking the first. Islands with airports are the exception here, not the rule.
The least touristy Greek islands, and what they cost in travel time
No airport, few connections, and a boat that runs to its own logic. Ranked by how few other islands they link to, which is a better measure of quiet than size:
Anyone weighing quiet greek islands against convenience should read those two lists as a single scale rather than as two categories. The islands with airports sit at one end, the least touristy greek islands at the other, and most trips work best with one of each.
What "quiet" means in practice, and when it stops being true
Quiet is a function of the calendar as much as of the island. The islands on this page are empty in June and in late September, and the smallest of them stay that way through July. August is different everywhere: Greek families take their own holidays then, the boats are full, and an island with forty rooms feels busy in a way that an island with four thousand does not. The quiet islands are not quiet in the second half of August. They are, however, cheap and half asleep by the last week of September, which is the best trade available on this coast.
The other variable is the boat. An island served twice a week is quiet because getting to it costs a day at each end, and that is a real cost, not a romantic one: it dictates the shape of the whole trip and it removes the option of changing your mind. An island with a runway can be quiet and still be reachable, which is why the airport list above is the useful half of this page. Where the two overlap — a small island, few beds, and a flight — the arithmetic is unusually good, and there are not many of them.
What you give up
Being honest about the trade: a bank, a pharmacy open on Sunday, a cash machine that is working, a doctor on the island, a choice of more than three places to eat, and any prospect of a taxi at eleven at night. On the smallest islands the shop closes when the owner has something else to do. None of that is a hardship over a week, and all of it is worth knowing before booking two.