Beaverton is about 4.2 times smaller than Seattle.

Seattle is approximately 217 sq km, while Beaverton (map shows its 13 named neighbourhoods; the area covers the whole city) is approximately 51 sq km, making Beaverton 23.52% the size of Seattle.
Tip: This to-scale comparison of Seattle vs. Beaverton uses the Mercator projection, which distorts the size of regions near the poles.
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