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  • Boulder item spriteold Boulder item sprite
  • Boulder placed
Stack digit 9.pngStack digit 9.pngStack digit 9.pngStack digit 9.png
Placeable✔️ (2 wide × 2 high)
Use time15 (Very fast)
RarityRarity level: 0
Research5 required
Projectile created
  • Boulder

Boulders are unique placeable 2×2 foreground objects, and are stationary when placed. When unsupported, they fall and begin to roll away. They pick up speed and damage players, enemies and NPCs along their path. Boulders will also begin to roll if mined with a pickaxe or drill, meaning that they cannot be picked up again once placed.

Boulders will roll across flat surfaces and down slopes, but will break and disappear on contact with an obstacle. They deal 120–160 / 240–320 / 360–480 damage to players (60–80 damage to NPCs, enemies, and critters) on contact.[1] Boulders pierce through an unlimited number of entities.

Boulder traps occur naturally in the Underground and Cavern layers, and consist of a single Boulder in the ceiling, supported by six (2×3) Active Stone Blocks wired to Pressure Plates. If a player walks onto the Pressure Plate, the Boulder falls down and begins rolling.



ResultIngredientsCrafting station
Desktop versionConsole versionMobile version only:
Heavy Work BenchHeavy Work Bench
Old-gen console versionNintendo 3DS version only:
Tinkerer's WorkshopTinkerer's Workshop
total: 2 row(s)

Used in

ResultIngredientsCrafting station
Bouncy BoulderBouncy BoulderHeavy Work BenchHeavy Work Bench
Boulder StatueBoulder StatueHeavy Work BenchHeavy Work Bench and Ecto Mist
Life Crystal BoulderLife Crystal Boulder
total: 3 row(s)


  • The direction in which Boulders start rolling depends on different factors:
    • Boulders always roll left, unless there is no space for them to go left, in which case they roll right.
    • Boulders started with a pickaxe or drill appear to roll the direction that will give them the longest roll time (e.g. if two walls are on either side of a long platform, placing the Boulder closer to one wall will cause it to roll the opposite direction).
  • The Boulder accelerates to a top speed of 36 mph over the course of 2.18 seconds.[2]
  • Once rolling, Boulders cause the same amount of damage regardless of their speed. A player or enemy hit by a Boulder that just began rolling will take just as much damage as they would from a fast-moving Boulder. This also means that players trying to mine it while touching it will be hit.
  • Like all other projectiles, the Boulder will break after rolling for one minute.
    • If moving along a flat strip of land, it can reach a maximum distance of 1559 tiles.
  • In For the worthy worlds, Boulders will release Mini Boulders when they break. These functions identical to the Boulder projectile, but smaller.
  • Boulders can be placed atop flat-surface furniture, such as bookcases, and can be stacked on each other. Mining the bottom Boulder causes all of them to fall and roll. Mining only the top Boulder causes only that one to roll off.
  • Boulders can activate red, green, and yellow (NPC-sensing) Pressure Plates by rolling over them.
  • Boulders are unable to fit through 2-tile high spaces in the Console version Console version.
  • It is possible for Boulders to roll uphill, as long as there is one flat block in between each sloped block.


  • In Expert and Master Modes, Boulder traps should be avoided at all costs, considering the deadly force of 280 / 420 average damage.
  • Boulders are effective when used along with Grenades against The Destroyer and Eater of Worlds.
  • Using Boulders is an efficient way to kill NPCs, should one wish to do that (for example, for getting their unique drops).
  • Players can detect Boulder traps "in the wild" by wielding a mechanism item such as a Pressure Plate (), by carrying a Mechanical Lens or its upgrade The Grand Design, or by using a Dangersense Potion. All except the last will allow the player to view placed wires, and the vertical wire with its 2×3 rectangle atop it is quite distinctive. Once detected, there are some basic ways to disarm them:
    • If approaching from above, the player can mine their way toward the top of the trap, and use a pickaxe to break the boulder from outside the sealed chamber.
    • From below, the player can make sure there is a slope downwards to the left, then trigger the plate from the right side and immediately dodge to the right.
    • Once the player has The Grand Design (or even just a Wire Cutter), they can easily disable the trap at a distance by cutting the vertical wire.
  • At full tilt, boulders roll faster than a running player with several speed boosts applied. Using a Hoverboard or Asphalt can help to overcome them.
  • Breaking the pressure plate will prevent the trap from triggering, but the Boulder will remain above, and may be encountered later.
    • As with other traps, the mechanisms (but not the Boulder) can be harvested for later use. The pressure plate and active stone can be taken with a pickaxe, but collecting the wire needs a Wire Cutter or upgrade thereof.
      • The pressure plate cannot be harvested due to the introduction of Orange Pressure Plates which now replace the previously used gray and brown pressure plates.
  • In Hardmode, the Active Stone Blocks do not change into their respective biome. Therefore, they can be much easier to spot and deactivate.



  • Desktop Damage from Boulders is now reduced by player defenses (Boulder damage previously ignored player defense).
  • Desktop 1.2.4: Fixed the crash when a Chest is placed above but not directly on a Boulder.
  • Desktop 1.2.3: Boulders with Chests on them no longer crash the game if the Boulder is hit.


  1. Information taken from the Desktop version Desktop source code, method Check2x2() in Terraria.WorldGen.cs. There may be inaccuracies, as the current Desktop version Desktop version is
  2. Information taken from the Desktop version Desktop source code, method AI() in Terraria.Projectile.cs. There may be inaccuracies, as the current Desktop version Desktop version is