Rotterdam is the second biggest city in The Netherlands after Amsterdam. It has about 660,000 inhabitants within the municipality. If you look at the whole urban area, the number of people would be around 1.2 million. Together with The Hague Rotterdam forms the Rotterdam-The Hague metropolitan area, which has a population of close to 2.5 million people. It’s also part of the Randstad (Edge City), a crescent-shaped conurbation in the central-western Netherlands. With a population of approximately 8.4 million people, The Randstad is one of the largest metropolitan regions in Europe. All 4 of the biggest cities in The Netherlands are part of The Randstad.
So if you take the urban area of the city, the population is about 1.2 million. It’s around the same size as the urban area of Amsterdam, so for Dutch standards that’s very large. But compared to some other urban areas worldwide, it’s rather small. The largest urban area in the world is Tokyo with a population of over 37 million people. Rotterdam’s urban area won’t even make the world’s top 100.
When you look at the area, the municipality has an area of 324.14 km2 (125.15 sq mi) of which about 1/3 is made up of water. The area is relatively large, since Rotterdam has the largest sea port of the Western World. The port stretches over 40 km (24.8 mi) from close to the city center all the way to the North Sea. The land area used by the port is about 80 km2 (30.8 sq mi).
So how big is Rotterdam? Big for Dutch standards, but on a world scale, not so big.