Redstone Comparator — Minecraft block

Redstone Comparator

Comparator measures signal strength and inventory contents — the analog brain of any complex redstone build.

Block ID minecraft:comparator
Mod Vanilla
Game versions
1.21

Description

Comparator is crafted from three redstone torches, one nether quartz, and three stone blocks arranged in the standard pattern. Unlike a repeater, this device does not boost the signal back to full strength — it instead measures and compares incoming signals, then outputs a precise analog level between zero and fifteen. This makes it the foundation of every signal-strength-aware build in the game.

The device has two modes, toggled by right-click. In compare mode (front torch off), it passes the rear-input signal through only if no side input is stronger; otherwise it outputs zero. In subtract mode (front torch on), it outputs the rear input minus the strongest side input. Most importantly, the device reads from container blocks placed behind it: a chest, hopper, brewing stand, or jukebox emits an analog signal proportional to fill level, enabling automated farms, item-counter displays, and disc players that trigger actions when a specific song plays.

Java & Bedrock Guide

How to use a Redstone Comparator in Minecraft

  1. 1

    Craft the comparator

    Place 3 redstone torches and 1 nether quartz in a T shape on top of a row of 3 stone blocks in the crafting grid to make one comparator.

  2. 2

    Place and orient it

    Set the comparator down so the small arrow on top points away from your circuit; that arrow marks the output side, while the two flat sides accept optional side inputs.

  3. 3

    Read a container

    Put the comparator directly behind a chest, barrel, furnace, or hopper so it outputs a signal from 1 to 15 scaled to how full the container is.

  4. 4

    Toggle subtract mode

    Right-click the comparator to light the front torch and switch to subtract mode, where the output equals the rear input minus the strongest side input.

Compare vs subtract

With the front torch off (compare mode) the comparator passes the rear signal only when no side input is stronger. With the front torch on (subtract mode) it subtracts the strongest side signal from the rear signal.

How to craft this block

Ingredients: Redstone Torch Redstone Torch x3 Nether Quartz Nether Quartz x1 Stone Stone x3
Crafting
Redstone Torch
Redstone Torch Nether Quartz Redstone Torch Stone Stone Stone
Redstone Comparator
1
Redstone Comparator

Related blocks

Frequently asked questions

How do you craft a comparator in Minecraft?

Place 3 redstone torches and 1 nether quartz in a T shape on top of 3 stone blocks in the crafting grid. This makes one redstone comparator.

What is the difference between compare and subtract mode?

In compare mode the comparator outputs the rear signal unless a side input is stronger. In subtract mode it outputs the rear signal minus the strongest side input. Right-click to switch; the front torch lights up in subtract mode.

Can a comparator read how full a chest is?

Yes. Placed behind a chest, barrel, hopper, furnace, or brewing stand, a comparator emits a signal from 1 to 15 proportional to how full the container is.

What is the difference between a comparator and a repeater?

A repeater restores a signal to full strength and adds delay, while a comparator keeps analog signal strength, can compare or subtract signals, and reads container fill levels.

Does the comparator work in both Java and Bedrock Edition?

Yes. The redstone comparator exists in both Java and Bedrock Edition with the same compare, subtract, and container-reading behaviour.

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