Belarus is around the same size as South Dakota.

South Dakota is approximately 196,540 sq km, while Belarus is approximately 207,600 sq km, making Belarus 6% larger than South Dakota. Meanwhile, the population of South Dakota is ~814,180 people (8.6 million more people live in Belarus).
Tip: This to-scale comparison of South Dakota vs. Belarus uses the Mercator projection, which distorts the size of regions near the poles.