REDSTONE COMPARATOR
A versatile component with two modes: compare mode (outputs back signal if back >= side) and subtract mode (outputs back - side). Can also read container fullness as an analog signal.
Crafting Recipe
3 Stone + 3 Redstone Torches + 1 Nether Quartz → 1 Redstone Comparator
Signal Behavior
Input
InputBack input and side inputs
Output
OutputCompare: back signal if back >= side (else 0). Subtract: back - max(sides), min 0.
Max Signal Strength
Max Signal Strength15
Delay
Delay1 redstone tick
Modes
- Compare mode (front torch off)
- Subtract mode (front torch on)
Overview: what the Redstone Comparator is and does
A versatile component with two modes: compare mode (outputs back signal if back >= side) and subtract mode (outputs back - side). Can also read container fullness as an analog signal.
As a transmission component its job is to carry, refresh, or reshape a signal as it moves between other blocks. It is the analog brain of redstone, the only component that can measure container fullness and do arithmetic on signal strengths.
The Redstone Comparator was added to Minecraft in 1.5 and everything described here reflects its behaviour in Java Edition 1.21.
How it works: the redstone mechanics
On the input side, back input and side inputs. On the output side, compare: back signal if back >= side (else 0). Subtract: back - max(sides), min 0..
In compare mode (front torch dark) it passes the back signal through unless a side input is stronger, in which case it outputs 0. In subtract mode (front torch lit) it outputs back minus the strongest side, floored at 0. Pointed out of a container it reads how full that container is as a signal from 0 to 15.
Timing-wise, factor in 1 redstone tick when you wire it into a sequenced circuit.
It can output a maximum signal strength of 15, which travels 15 blocks through bare redstone dust before fading to nothing.
It operates in the following modes: compare mode (front torch off) and subtract mode (front torch on).
How to set it up
- 1Craft the Redstone Comparator: 3 Stone + 3 Redstone Torches + 1 Nether Quartz → 1 Redstone Comparator.
- 2Decide where the signal needs to start or land, then place the Redstone Comparator against a solid surface so it can feed the rest of your circuit.
- 3Wire dust into its input side and read the refreshed or modified signal off its output side, keeping its facing in mind.
- 4Test in a creative-mode plot first: trigger the input and confirm the Redstone Comparator behaves exactly as the timing above predicts before committing it to a survival build.
Uses & applications
- ▸Container fullness detection
- ▸Analog signal processing
- ▸Subtraction circuits
- ▸Item sorting
- ▸Signal comparison
Tips & common mistakes
- !Confusing compare vs subtract mode
- !Side inputs override if stronger in compare mode
- !Reading containers requires specific placement
- !Mixing up compare and subtract mode is the classic comparator bug — check whether the little front torch is lit before blaming your wiring.
Redstone Comparator FAQ
What is the Redstone Comparator used for in Minecraft redstone?
The Redstone Comparator is most often used for container fullness detection, analog signal processing, subtraction circuits, and item sorting. As a transmission component its job is to carry, refresh, or reshape a signal as it moves between other blocks.
What signal strength does the Redstone Comparator output?
Compare: back signal if back >= side (else 0). Subtract: back - max(sides), min 0. Its maximum signal strength is 15.
How do you craft the Redstone Comparator?
3 Stone + 3 Redstone Torches + 1 Nether Quartz → 1 Redstone Comparator. It was introduced in 1.5.
Does the Redstone Comparator add any delay to a circuit?
Yes — 1 redstone tick. Account for that timing when chaining it with other components, especially in clocks and fast doors.
How does a comparator read a chest?
Point the comparator's back into the chest (or place it one block away facing the chest). It outputs a signal from 0 (empty) to 15 (full) scaled to how full the container is, accounting for stack sizes. A single item in a large double chest produces signal 1.