Sydney is about 4.2 times bigger than Fort Worth.

Fort Worth (map shows its 16 named neighbourhoods; the area covers the whole city) is approximately 911 sq km, while Sydney (the 30 councils of metropolitan Sydney, without the Blue Mountains, Hawkesbury, Wollondilly and the Central Coast) is approximately 3,810 sq km, making Sydney 318% larger than Fort Worth.
Tip: This to-scale comparison of Fort Worth vs. Sydney uses the Mercator projection, which distorts the size of regions near the poles.
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