Pitcairn Islands is about 3.8 times smaller than District of Columbia.

District of Columbia is approximately 177 sq km, while Pitcairn Islands is approximately 47 sq km, making Pitcairn Islands 26.55% the size of District of Columbia. Meanwhile, the population of District of Columbia is ~601,723 people (601,673 fewer people live in Pitcairn Islands).
Tip: This to-scale comparison of District of Columbia vs. Pitcairn Islands uses the Mercator projection, which distorts the size of regions near the poles.