Australia is approximately 7,741,220 sq km, while Saudi Arabia is approximately 2,149,690 sq km, making Saudi Arabia 27.77% the size of Australia. Meanwhile, the population of Australia is ~25.5 million people (8.7 million more people live in Saudi Arabia).
This to-scale map shows a size comparison of Australia compared to Saudi Arabia. For more details, see an in-depth quality of life comparison of Saudi Arabia vs. Australia using our country comparison tool.