Pitcairn Islands is about 24 times bigger than Monaco.

Monaco is approximately 2 sq km, while Pitcairn Islands is approximately 47 sq km, making Pitcairn Islands 2,250% larger than Monaco. Meanwhile, the population of Monaco is ~31,400 people (31,350 fewer people live in Pitcairn Islands).
Tip: This to-scale comparison of Monaco vs. Pitcairn Islands uses the Mercator projection, which distorts the size of regions near the poles.