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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
Projectiles created
  • Boulder
  • Boulder

The Boulder is a unique placeable foreground object that is stationary when placed. When unsupported, it falls and begins to roll away, picking up speed and damaging players, enemies, critters, and NPCs along its path. Boulders will also begin to roll if hit 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 140 / 280 / 420 damage to players (70 damage to NPCs, enemies, and critters) and inflict a knockback of 10 (Extremely strong) on contact.[1] While rolling, Boulders can pierce through an unlimited number of entities and accelerate to a top speed of 36 mph over the course of 2.17 seconds.[2]

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 while wired to a Orange Pressure Plate. Once a player walks onto the Pressure Plate, the Boulder falls down and begins rolling.

In For the worthy(Desktop, Console and Mobile versions) and Get fixed boi(Desktop, Console and Mobile versions) worlds, Boulders will will release 2–4 miniature Boulders when they break. These function identical to the Boulder projectile, but are smaller and deal 75% base damage (105 / 210 / 315).



ResultIngredientsCrafting station
Desktop versionConsole versionMobile version only:
Heavy Work BenchHeavy Work Bench(Desktop, Console, Old-gen console and Mobile versions)
Old-gen console versionNintendo 3DS version only:
Tinkerer's WorkshopTinkerer's Workshop

Used in

ResultIngredientsCrafting station
Bouncy BoulderBouncy Boulder(Desktop, Console and Mobile versions)Heavy Work BenchHeavy Work Bench(Desktop, Console, Old-gen console and Mobile versions)
Boulder StatueBoulder Statue(Desktop, Console and Mobile versions)Heavy Work BenchHeavy Work Bench(Desktop, Console, Old-gen console and Mobile versions) and Ecto Mist(Desktop, Console and Mobile versions)
Life Crystal BoulderLife Crystal Boulder(Desktop, Console and Mobile versions)


  • The direction in which Boulders start rolling depends on different factors:
    • (Old-gen console and 3DS versions) Boulders always roll left, unless there is no space for them to go left, in which case they roll right.
    • (Desktop, Console and Mobile versions) Boulders started with a pickaxe or drill appear to roll in the direction that will give them the longest amount of time to roll (e.g. if two walls are on either side of a long platform, placing it closer to one wall will cause it to roll the opposite direction).
  • Once rolling, Boulders deal the same amount of damage regardless of their speed. A player or enemy hit by a Boulder that had just begun rolling will take just as much damage as they would from a Boulder moving at a higher speed. This also means that players trying to mine a Boulder while touching it will take damage.
  • Like all other projectiles, the Boulder will break after rolling for one minute.
    • If moving along a flat strip of land, this allows it to roll a maximum distance of 1548.6 tiles.[3]
  • Boulders can be placed atop flat-surface furniture, such as tables or bookcases, and can be stacked on top of each other. Mining the bottom Boulder causes all of them to fall and roll, while only the topmost Boulder only causes 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(Desktop, Console and Mobile versions) and Master Modes(Desktop, Console and Mobile versions), 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 ((Old-gen console and 3DS versions)), by carrying a Mechanical Lens(Desktop, Console and Mobile versions) or its upgrade The Grand Design(Desktop, Console and Mobile versions), 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.
  • 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.
  2. Information taken from the Desktop version Desktop source code, method AI() in Terraria.Projectile.cs. The relevant part is the aiStyle == 25 block.
  3. 1 minute total = 3600 ticks. During the accelerating phase (130 ticks), it reaches 487.5 pixels. During the remaining 3470 ticks (when it is moving at a constant speed), it reaches 24290 pixels. 487.5 + 24290 = 24777.5 pixels total. See this WolframAlpha plot for a visualization. Divide by 16 to obtain tiles.