Total surface area of Earth is ~500,000,000 km^2
Total land area of Earth is ~150,000,000 km^2 (~.29 Earth)
Australia's land area is ~7,500,000 km^2 (~.015 Earth, 5% of land area)
Moon surface area is ~38,000,000 km^2 (~0.074 Earth, 25% of land area)