Nigeria is about 2.1 times bigger than Iraq.

Iraq is approximately 438,317 sq km, while Nigeria is approximately 923,768 sq km, making Nigeria 111% larger than Iraq. Meanwhile, the population of Iraq is ~40.5 million people (184.6 million more people live in Nigeria).
Tip: This to-scale comparison of Iraq vs. Nigeria uses the Mercator projection, which distorts the size of regions near the poles.