Guam is about 1.6 times bigger than Grenada.

Grenada is approximately 344 sq km, while Guam is approximately 544 sq km, making Guam 58% larger than Grenada. Meanwhile, the population of Grenada is ~113,949 people (55,137 more people live in Guam).
Tip: This to-scale comparison of Grenada vs. Guam uses the Mercator projection, which distorts the size of regions near the poles.