Guinea is approximately 245,857 sq km, while Sierra Leone is approximately 71,740 sq km, making Sierra Leone 29.18% the size of Guinea. Meanwhile, the population of Guinea is ~12.5 million people (5.9 million fewer people live in Sierra Leone).
This to-scale map shows a size comparison of Guinea compared to Sierra Leone. For more details, see an in-depth quality of life comparison of Sierra Leone vs. Guinea using our country comparison tool.