Luxembourg is about 15 times bigger than District of Columbia.

District of Columbia is approximately 177 sq km, while Luxembourg is approximately 2,586 sq km, making Luxembourg 1,361% larger than District of Columbia. Meanwhile, the population of District of Columbia is ~601,723 people (48,641 more people live in Luxembourg).
Tip: This to-scale comparison of District of Columbia vs. Luxembourg uses the Mercator projection, which distorts the size of regions near the poles.