Australia dwarfs Iran: about 7,706,009 km² km² against 1,622,847 km² km². At true size Australia is about 4.7× larger — the whole of Iran fits into Australia roughly 4 times.
Australia sits in Oceania, Iran in Asia. On the old Mercator map the latitude gap distorted how large each felt beside the other; at true size the answer is simply 4.7×.
The old Mercator map treated both about equally (1.2× vs 1.4× inflation), so at least their relative sizes were preserved — even if both were drawn at the wrong absolute scale.
Iran fits 4× into Australia.