Niger is about 5 times bigger than Guinea.

Guinea is approximately 245,857 sq km, while Niger is approximately 1,267,000 sq km, making Niger 415% larger than Guinea. Meanwhile, the population of Guinea is ~15.1 million people (12.8 million more people live in Niger).
Tip: This to-scale comparison of Guinea vs. Niger uses the Mercator projection, which distorts the size of regions near the poles.
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