Vermont is about 8 times smaller than South Dakota.

South Dakota is approximately 196,540 sq km, while Vermont is approximately 23,956 sq km, making Vermont 12.19% the size of South Dakota. Meanwhile, the population of South Dakota is ~814,180 people (188,439 fewer people live in Vermont).
Tip: This to-scale comparison of South Dakota vs. Vermont uses the Mercator projection, which distorts the size of regions near the poles.