Tonga is about 4.2 times bigger than District of Columbia.

District of Columbia is approximately 177 sq km, while Tonga is approximately 747 sq km, making Tonga 322% larger than District of Columbia. Meanwhile, the population of District of Columbia is ~601,723 people (496,206 fewer people live in Tonga).
Tip: This to-scale comparison of District of Columbia vs. Tonga uses the Mercator projection, which distorts the size of regions near the poles.