District of Columbia is about 656 times smaller than Pennsylvania.

Pennsylvania is approximately 116,075 sq km, while District of Columbia is approximately 177 sq km, making District of Columbia 0.15% the size of Pennsylvania. Meanwhile, the population of Pennsylvania is ~12.7 million people (12.1 million fewer people live in District of Columbia).
Tip: This to-scale comparison of Pennsylvania vs. District of Columbia uses the Mercator projection, which distorts the size of regions near the poles.