Karachi is about 11 times bigger than Rotterdam.

Rotterdam (map shows its 22 named neighbourhoods; the area covers the whole city) is approximately 319 sq km, while Karachi is approximately 3,527 sq km, making Karachi 1,004% larger than Rotterdam.
Tip: This to-scale comparison of Rotterdam vs. Karachi uses the Mercator projection, which distorts the size of regions near the poles.
Our free app, MapSize by MyLifeElsewhere — compare any two places, to scale on your mobile device.