Greece is approximately 131,957 sq km, while Belgium is approximately 30,528 sq km, making Belgium 23.13% the size of Greece. Meanwhile, the population of Greece is ~10.6 million people (1.1 million more people live in Belgium).
This to-scale map shows a size comparison of Greece compared to Belgium. For more details, see an in-depth quality of life comparison of Belgium vs. Greece using our country comparison tool.