Oakland is about 19 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 Oakland (map shows its 131 named neighbourhoods; the area covers the whole city) is approximately 202 sq km, making Oakland 5.3% the size of Sydney.
Tip: This to-scale comparison of Sydney vs. Oakland uses the Mercator projection, which distorts the size of regions near the poles.
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