Denver is about 1.3 times smaller than Warsaw.

Warsaw is approximately 517 sq km, while Denver is approximately 396 sq km, making Denver 76.66% the size of Warsaw.
Tip: This to-scale comparison of Warsaw vs. Denver 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.