Los Angeles is about 3.3 times bigger than Las Vegas.

Las Vegas (map shows its 26 named neighbourhoods; the area covers the whole city) is approximately 367 sq km, while Los Angeles (including the city proper only) is approximately 1,215 sq km, making Los Angeles 231% larger than Las Vegas.
Tip: This to-scale comparison of Las Vegas vs. Los Angeles uses the Mercator projection, which distorts the size of regions near the poles.
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