Australia dwarfs Peru: about 7,706,009 km² km² against 1,296,279 km² km². At true size Australia is about 5.9× larger — the whole of Peru fits into Australia roughly 5 times.
Australia sits in Oceania, Peru in South America. On the old Mercator map the latitude gap distorted how large each felt beside the other; at true size the answer is simply 5.9×.
The old Mercator map treated both about equally (1.2× vs 1× inflation), so at least their relative sizes were preserved — even if both were drawn at the wrong absolute scale.
Peru fits 5× into Australia.