Saint Kitts and Nevis is about 1.5 times bigger than District of Columbia.

District of Columbia is approximately 177 sq km, while Saint Kitts and Nevis is approximately 261 sq km, making Saint Kitts and Nevis 47% larger than District of Columbia. Meanwhile, the population of District of Columbia is ~601,723 people (547,235 fewer people live in Saint Kitts and Nevis).
Tip: This to-scale comparison of District of Columbia vs. Saint Kitts and Nevis uses the Mercator projection, which distorts the size of regions near the poles.