- Small - 4300 blocks wide and 1200 blocks high, sky limit about 360-370 blocks above underground level.
- Medium - 6300 blocks wide and 1800 blocks high, sky limit about 450-600 blocks above underground level.
- Large - 8400 blocks wide and 2400 blocks high, sky limit about 800-900 blocks above underground level.
Sky, ground level, stone layer and underground layer (underground jungle being part of it) seem to be affected from scaling while size of the dungeon (not counting the corridor leading down) and Underworld (always at 180-200 blocks from the lower border of the world) seem to be affected only slightly. Depth of the Corruption chasms are also affected only a little bit with a small chance of spawning chasms down to the underground level, no matter how deep it is.
It also seems that in larger worlds, resources are much farther apart from each other in comparison to the smaller ones. This means that in smaller worlds, resources are much easier to locate and mine - see the map viewer fragments in the gallery below for comparison. On a large map, corruptions can (rarely?) go down deep, as well reaching to the Underworld, or you can get close to getting to the underworld.
World sizes can be changed from programs similar to TEdit.
Shots were taken from the zone 600x450 blocks at corrupted area for better comparison.