Ireland is about 397 times bigger than District of Columbia.

District of Columbia is approximately 177 sq km, while Ireland is approximately 70,273 sq km, making Ireland 39,602% larger than District of Columbia. Meanwhile, the population of District of Columbia is ~601,723 people (4.7 million more people live in Ireland).
Tip: This to-scale comparison of District of Columbia vs. Ireland uses the Mercator projection, which distorts the size of regions near the poles.