District of Columbia is about 5 times smaller than Sao Tome and Principe.

Sao Tome and Principe is approximately 964 sq km, while District of Columbia is approximately 177 sq km, making District of Columbia 18.36% the size of Sao Tome and Principe. Meanwhile, the population of Sao Tome and Principe is ~217,164 people (384,559 more people live in District of Columbia).
Tip: This to-scale comparison of Sao Tome and Principe vs. District of Columbia uses the Mercator projection, which distorts the size of regions near the poles.