Des Moines is about 4.5 times bigger than Beaverton.

Beaverton (map shows its 13 named neighbourhoods; the area covers the whole city) is approximately 51 sq km, while Des Moines (map shows its 58 named neighbourhoods; the area covers the whole city) is approximately 228 sq km, making Des Moines 347% larger than Beaverton.
Tip: This to-scale comparison of Beaverton vs. Des Moines uses the Mercator projection, which distorts the size of regions near the poles.
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