Ho Chi Minh City is about 1.8 times bigger than Sydney.

Sydney (the 30 councils of metropolitan Sydney, without the Blue Mountains, Hawkesbury, Wollondilly and the Central Coast) is approximately 3,810 sq km, while Ho Chi Minh City is approximately 6,773 sq km, making Ho Chi Minh City 78% larger than Sydney.
Tip: This to-scale comparison of Sydney vs. Ho Chi Minh City uses the Mercator projection, which distorts the size of regions near the poles.
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