District of Columbia is about 2.2 times smaller than Saint Helena, Ascension, and Tristan da Cunha.

Saint Helena, Ascension, and Tristan da Cunha is approximately 394 sq km, while District of Columbia is approximately 177 sq km, making District of Columbia 44.92% the size of Saint Helena, Ascension, and Tristan da Cunha. Meanwhile, the population of Saint Helena, Ascension, and Tristan da Cunha is ~7,925 people (593,798 more people live in District of Columbia).
Tip: This to-scale comparison of Saint Helena, Ascension, and Tristan da Cunha vs. District of Columbia uses the Mercator projection, which distorts the size of regions near the poles.