Atlanta is about 1.5 times smaller than Warsaw.

Warsaw is approximately 517 sq km, while Atlanta (map shows its 114 named neighbourhoods; the area covers the whole city) is approximately 350 sq km, making Atlanta 67.76% the size of Warsaw.
Tip: This to-scale comparison of Warsaw vs. Atlanta 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.