San Bernardino is about 2.2 times smaller than Atlanta.

Atlanta (map shows its 114 named neighbourhoods; the area covers the whole city) is approximately 350 sq km, while San Bernardino (map shows its 50 named neighbourhoods; the area covers the whole city) is approximately 161 sq km, making San Bernardino 45.9% the size of Atlanta.
Tip: This to-scale comparison of Atlanta vs. San Bernardino uses the Mercator projection, which distorts the size of regions near the poles.
Our free app, MapSize by MyLifeElsewhere — compare any two places, to scale on your mobile device.