Most visitors give Rotterdam an afternoon. They come up out of Centraal, photograph the Markthal, walk ten minutes to the Cube Houses, conclude that the city is a collection of buildings rather than a place, and take the train back to Amsterdam before dinner. That is a planning failure, not a verdict.
Rotterdam's centre was destroyed in May 1940 and rebuilt without nostalgia, so its pleasures are not arranged in a tidy historic ring the way Delft's or Bruges's are. They sit in pockets on two banks of a wide, working river, and the order you take them in decides whether the city reads as coherent or scattered. Almost every disappointed visitor has made the same mistake: crossing the Maas three or four times in a day, losing twenty minutes to each crossing, and never spending long enough on either bank to feel it.
The short answer on length is two full days for the city and a third for everything the bombing missed. The third day is the one that changes people's minds.
How Many Days Rotterdam Is Actually Worth
One day works, but only as a day trip with a fixed route and no museum ambitions. Rotterdam sits roughly forty minutes from Amsterdam on the fast Intercity Direct service and about a quarter of an hour from Delft, so plenty of people arrive this way. There is a route for it further down, and it involves skipping Museumpark altogether.
Two days is the honest minimum for the city itself, and the structure is obvious once you look at a map: one bank per day. North bank on day one, south bank on day two, one deliberate crossing in between rather than four accidental ones.
Three days is where Rotterdam stops being a set of landmarks. The third day buys you Delfshaven and Rotterdam Noord, the parts that either survived the war or grew up afterwards without architects watching, or it buys you the delta the city sits in.
Four or more only pays if you are using Rotterdam as a base, which is a genuinely good idea. Kinderdijk, Dordrecht, Delft and Den Haag are all inside an hour, and a mid-range double room in Rotterdam typically costs noticeably less than the equivalent in Amsterdam. If your trip is really a South Holland trip, sleep here.
On timing: late spring through early autumn is the stretch that suits this itinerary best, and not only for the weather. The Maritime Museum's outdoor harbour of historic ships and cranes generally closes for the winter months, the Van Nelle Factory runs tours on both weekend days in the warmer half of the year and typically Saturdays only in the colder half, and the terraces on Katendrecht and the open-deck water taxi are a different proposition in June than in February. Wind coming off the Maas makes any Rotterdam day feel several degrees colder than the forecast suggests.
The Crossing Is the Decision
Getting around is easy and cheap, which is why so many people waste it. The RET network runs five metro lines lettered A to E, plus trams and buses, and the Netherlands has been fully contactless for years: tap in and tap out with a Visa, Mastercard or Maestro card or a phone using OVpay, and the fare is calculated for you. If you expect a lot of short hops, a one-day RET ticket costs around EUR 12 for an adult at the time of writing, and a regional day ticket covering the wider province and the waterbus runs closer to EUR 17.50. Do the sums honestly, because two or three tapped journeys a day will not beat pay-as-you-go.
Walking distances are shorter than they look. Centraal to the Markthal is a walk of about twenty minutes, the Markthal to the foot of the Erasmusbrug maybe fifteen, and the bridge itself takes eight to ten minutes to cross on foot. Bikes are everywhere and the infrastructure is excellent, though the centre's wide boulevards are less charming to cycle than Utrecht's canals.
The thing worth planning around is the water taxi: small, fast, open-backed boats that connect more than fifty jetties along the Maas and into the harbours, bookable through an app. On the short central crossings expect to pay a few euros a head; longer runs into the port cost considerably more. Treat one crossing a day as part of the itinerary rather than as transport, and time it for dusk.