Brunei is about 123 times bigger than Pitcairn Islands.

Pitcairn Islands is approximately 47 sq km, while Brunei is approximately 5,765 sq km, making Brunei 12,166% larger than Pitcairn Islands. Meanwhile, the population of Pitcairn Islands is ~50 people (478,004 more people live in Brunei).
Tip: This to-scale comparison of Pitcairn Islands vs. Brunei uses the Mercator projection, which distorts the size of regions near the poles.