Austin is about 1.7 times smaller than Saint Petersburg.

Saint Petersburg is approximately 1,439 sq km, while Austin (map shows its 70 named neighbourhoods; the area covers the whole city) is approximately 829 sq km, making Austin 57.58% the size of Saint Petersburg.
Tip: This to-scale comparison of Saint Petersburg vs. Austin uses the Mercator projection, which distorts the size of regions near the poles.
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