New Zealand is about 1.4 times bigger than South Dakota.

South Dakota is approximately 196,540 sq km, while New Zealand is approximately 268,838 sq km, making New Zealand 37% larger than South Dakota. Meanwhile, the population of South Dakota is ~814,180 people (4.2 million more people live in New Zealand).
Tip: This to-scale comparison of South Dakota vs. New Zealand uses the Mercator projection, which distorts the size of regions near the poles.