Saint Barthelemy is about 5,758 times smaller than Illinois.

Illinois is approximately 143,961 sq km, while Saint Barthelemy is approximately 25 sq km, making Saint Barthelemy 0.02% the size of Illinois. Meanwhile, the population of Illinois is ~12.8 million people (12.8 million fewer people live in Saint Barthelemy).
Tip: This to-scale comparison of Illinois vs. Saint Barthelemy uses the Mercator projection, which distorts the size of regions near the poles.