San Antonio is about 1.3 times smaller than Houston.

Houston is approximately 1,659 sq km, while San Antonio (map shows its 401 named neighbourhoods; the area covers the whole city) is approximately 1,292 sq km, making San Antonio 77.91% the size of Houston.
Tip: This to-scale comparison of Houston vs. San Antonio uses the Mercator projection, which distorts the size of regions near the poles.
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