World size

World size refers to the size of a Terraria world. Upon creation, on the, the player can select either "small", "medium", or "large" for the size of the world to generate. On the, the player can select either "normal" or "expanded". The worlds are smaller due to less memory. A "expanded" world is the equivalent of a  "small" world.

Dimensions of the different map sizes are as follows: (one tile = two feet)

World generation limits
World size has a notable impact on how many of a certain structure may be generated in the world. The values listed below are the theoretical maximums and not a guaranteed count. Although unlikely, some large structures and biomes can be skipped if no proper placement is found. Additionally, some smaller structures can be overwritten by other structures, or be blocked by other nearby structures. The ranges listed are based on chance factors during generation and not on observed data.

World size comparison
Different world sizes may be better suited for different purposes. Players may find that creating many small worlds may be more efficient than creating large worlds due to the amount of memory needed.

Advantages of small worlds
Everything is closer and quicker to reach:


 * Getting to specific locations like the Dungeon, Jungle and Oceans requires less walking.
 * Building skybridges, subways, teleporters, and hellevators is quicker and less costly.
 * Less digging is required to reach the Underworld.
 * Floating Islands are lower and therefore easier to find.
 * Wyverns spawn closer to the ground and are therefore easier to farm.
 * Note though that this can be a double-edged sword as simply being above the treetops can trigger them to spawn.
 * Ores are potentially easier to find.
 * The Corruption/Crimson/Hallow is easier to control.
 * It is easier to find the Jungle Temple.
 * Retrieving liquids such as water and lava with buckets or pumps is quicker and easier.
 * Meteors are easier to locate.
 * The world generates, saves, and loads faster.

Advantages of large worlds
There is more space to build and explore:


 * Layer and biome transitions are more gradual.
 * The Wyvern spawn level is higher, making above-ground housing safer at low altitudes.
 * Conversely, there is more below-ground space that counts as surface, which can be used for farms of "surface-only" plants like trees or mushrooms.
 * There is a greater chance of having lakes or pools big enough for fishing.
 * The Underworld is longer, potentially giving more time to defeat the Wall of Flesh.
 * The Celestial Towers will be more spread out, reducing the likelihood of the player's base and NPC homes being overrun.
 * The evil biome or hallow is less likely to spawn near the Jungle, for the same reason as above.
 * The surface terrain tends to be more varied and interesting.
 * Abandoned Mine Tracks are longer and more common.

There is more "stuff" in the world:


 * There are more total chests and pots underground per world.
 * This includes terrain features and structures such as Jungle Shrines, Enchanted Sword Shrines, and Floating Islands, as well as a higher chance of generating Pyramids.
 * There are more materials, including ore and wood. For example, there is more wood already grown and more room to plant trees.
 * The Dungeon has a greater chance to have all three Dungeon Wall types.
 * There are more Evil Biome chasms. This means that there are more Shadow Orbs/Crimson Hearts to destroy, which drop unique and valuable items. There are also more Demon Altars, which means there would be more Hardmode ores to generate.
 * The Jungle Temple possibly contains more traps and Lihzahrd Power Cells.
 * More meteorite crash sites can be in the world at one time.
 * Like with Wyvern spawn heights, this can also be a double-edged sword as a higher number of meteorite blocks are required in the world to prevent more meteorites from spawning and potentially destroying landscapes or player built structures.

Trivia

 * Using server command lines with the  parameter, medium sized worlds generate 6300 tiles wide instead of 6400, which is exactly 1.5x larger than small sized worlds.