Seattle is about 1.3 times bigger than Irvine.

Irvine (map shows its 24 named neighbourhoods; the area covers the whole city) is approximately 170 sq km, while Seattle is approximately 217 sq km, making Seattle 28% larger than Irvine.
Tip: This to-scale comparison of Irvine vs. Seattle uses the Mercator projection, which distorts the size of regions near the poles.
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