Spain is approximately 505,370 sq km, while Belgium is approximately 30,528 sq km, making Belgium 6.04% the size of Spain. Meanwhile, the population of Spain is ~50.0 million people (38.3 million fewer people live in Belgium).
This to-scale map shows a size comparison of Spain compared to Belgium. For more details, see an in-depth quality of life comparison of Belgium vs. Spain using our country comparison tool.