Belize is around the same size as New Hampshire.

New Hampshire is approximately 23,227 sq km, while Belize is approximately 22,966 sq km, making Belize 98.88% the size of New Hampshire. Meanwhile, the population of New Hampshire is ~1.3 million people (904,083 fewer people live in Belize).
Tip: This to-scale comparison of New Hampshire vs. Belize uses the Mercator projection, which distorts the size of regions near the poles.