Atlanta is about 11 times smaller 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 Atlanta (map shows its 114 named neighbourhoods; the area covers the whole city) is approximately 350 sq km, making Atlanta 9.2% the size of Sydney.
Tip: This to-scale comparison of Sydney vs. Atlanta uses the Mercator projection, which distorts the size of regions near the poles.
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