Terraria: How to Get the Ruler From the Goblin Tinkerer

The Ruler is a small measuring tool in Terraria that overlays measurement lines on your screen so you can count blocks while building. It comes from a single vendor, the Goblin Tinkerer, and that vendor only becomes available after one specific event. Once you know the sequence, picking it up takes only a few silver coins.

Quick answer: Defeat a Goblin Army in your world, find and free the bound Goblin Tinkerer underground, then buy the Ruler from his Shop tab for about 10 silver.

Requirements before you can buy the Ruler

The Ruler has no crafting recipe and no drop source. It is sold only by the Goblin Tinkerer, so the entire task depends on unlocking that NPC. He does not appear in your world until two things happen in order.

A Goblin Army invasion must be defeated in your world.
You must then find the Goblin Tinkerer, who spawns bound somewhere underground, and free him.

How to unlock the Goblin Tinkerer

Beat a Goblin Army. This invasion event has to be cleared in your current world before the Tinkerer can spawn. Until you defeat one, he will not exist underground.

Explore and mine underground to locate him. After the army is defeated, the Goblin Tinkerer spawns randomly as a bound NPC below the surface. Digging through caves and tunnels is the most reliable way to run into him.

Interact with the bound Goblin Tinkerer to release him. Once freed, he moves in as a housed NPC, the same way other town characters do, provided you have suitable housing for him.

Buy the Ruler from the Goblin Tinkerer

Talk to the Goblin Tinkerer once he is living in your town. His dialogue box appears at the top of the screen with the options Shop, Close, Reforge, and Happiness.

Click the Shop option to open his inventory on the left side of the screen. The Ruler sits among his stock alongside items like the Grappling Hook, Rocket Boots, Spiky Ball, Tinkerer’s Workshop, and Toolbelt.

Hover over the Ruler to confirm it, then click to buy it. The base price is about 10 silver, though the exact cost shifts slightly with the Tinkerer’s happiness. It drops straight into your inventory once purchased.

You know it worked when the Ruler icon lands in an inventory slot and the shop menu deducts the coins. From there you can close both menus and start using it.

What the Ruler does and how it works by version

The Ruler’s job is to help you place blocks precisely. It draws non-solid, white measurement lines across the screen so you can read off widths, heights, and areas while building. It gives no combat or stat bonuses on its own beyond changing what you see.

How it behaves depends on which version of Terraria you play. On modern platforms it is technically a weapon you toggle, while on older platforms it is a pure informational accessory.

Version	Item type	Buy price	How measurements activate
PC, Console, Mobile, tModLoader	Autoswinging shortsword	10 silver	“Ruler On” / “Ruler Off” toggle in the upper-left of the inventory
Old-gen console, Windows Phone, Old Chinese, 3DS, tModLoader Legacy	Informational accessory	1 gold	Equip it in an accessory slot

On PC, Console, Mobile, and tModLoader, the Ruler swings as a shortsword that deals 12 melee damage with a 4% critical chance, very fast use speed, and extremely weak knockback. It is the only autoswinging shortsword in the game. By the time the Goblin Tinkerer is available, though, you will almost always have far stronger weapons, so its value is in measuring rather than fighting.

Note: The Ruler sells back for one third of its buy value rather than the usual one fifth, and it can still be reforged for accessory-style modifiers. Its best modifier is Legendary.

Using the Ruler to craft The Grand Design

The Ruler is also a crafting ingredient for The Grand Design, a wiring tool. If you plan to make that item, keep your Ruler rather than selling it.

Result	Ingredients	Crafting station
The Grand Design	Multicolor Wrench, Mechanical Lens, Ruler, 60 Wire	Tinkerer’s Workshop

With the Goblin Tinkerer housed and a handful of silver spent, the Ruler is yours to line up clean, evenly spaced builds. It will not construct anything for you, but it takes the guesswork out of measuring blocks while you plan and place them.