Redstone Comparator

Powered Subtracting Redstone Comparator (S) JE5.png

Subtracting Redstone Comparator (S) BE.png

Powered Subtracting Redstone Comparator (S) BE.png

Renewable	Yes
Stackable	Yes (64)
Tool	Any tool
Blast resistance	0
Hardness	0
Luminant	No
Transparent	Yes
Flammable	No
Catches fire from lava	No

A redstone comparator is a block used in redstone circuits to maintain, compare, or subtract signal strength, or to measure certain block states (primarily the fullness of containers).

Obtaining[edit]

Breaking[edit]

A redstone comparator can be broken instantly with any tool, including the player's fist, and drops itself as an item.

Block	Redstone Comparator
Hardness	0
Breaking time
Default	0.05

A redstone comparator is removed and dropped as an item if:

its attachment block is moved, removed, or destroyed;
water flows into its space;‌^{[Java Edition only]}
or a piston tries to push it or moves a block into its space.

If lava flows into a redstone comparator's space, the redstone comparator is destroyed without dropping itself as an item.

Crafting[edit]

Ingredients	Crafting recipe
Redstone Torch + Nether Quartz + Stone

Usage[edit]

A redstone comparator can be placed on the top of any opaque block with a solid full-height top surface (including upside-down slabs and upside-down stairs). In Bedrock Edition, a comparator can also be placed on walls and fences. For more information about placement on transparent blocks, see Opacity/Placement.

The redstone comparator has a front and a back — the arrow on the top of the comparator points to the front. When placed, the comparator faces away from the player. The comparator has two miniature redstone torches at the back and one at the front. The back torches turn on when the comparator's output is greater than zero (the arrow on top also turns red). The front torch has two states that can be toggled by using the comparator:

Down and unpowered (indicating the comparator is in "comparison mode")
Up and powered (indicating the comparator is in "subtraction mode")

The redstone comparator can take a signal strength input from its rear as well as from both sides. Side inputs are accepted only from redstone dust, redstone blocks, redstone repeaters and other comparators. The redstone comparator's front is its output.

It takes 1 redstone tick (2 game ticks, or 0.1 seconds barring lag) for signals to move through a redstone comparator, either from the rear or from the sides. This applies to changing signal strengths as well as simply to turning on and off. Redstone comparators usually do not respond to 1-tick fluctuations of power or signal strength — for example, a 1-clock input is treated as always off from the side, and always on from the rear.

The redstone comparator has four functions: maintain signal strength, compare signal strength, subtract signal strength, and measure certain block states (primarily the fullness of containers).

Maintain signal strength[edit]

A redstone comparator with no powered sides outputs the same signal strength as its rear input.

Compare signal strength[edit]

Comparators in comparison mode.

A redstone comparator in comparison mode (front torch down and unpowered) compares its rear input to its two side inputs. If either side input is greater than the rear input, the comparator output turns off. If neither side input is greater than the rear input, the comparator outputs the same signal strength as its rear input.

Formula: Output = Rear × (Left <= Rear AND Right <= Rear)

Subtract signal strength[edit]

A redstone comparator in subtraction mode (front torch up and powered) subtracts the signal strength of the higher side input from the signal strength of the rear input.

Formula: Output = max(Rear - max(Left, Right), 0)

For example: if the signal strength is 6 at the left input, 7 at the right input and 4 at the rear, the output signal has a strength of max(4 - max(6, 7), 0) = max(4-7, 0) = max(-3, 0) = 0.

If the signal strength is 9 at the rear, 2 at the right input and 5 at the left input, the output signal has a strength of max(9 - max(2, 5), 0) = max(9-5, 0) = 4.

Measure block state[edit]

A redstone comparator can measure the fullness of a chest, as well as other block states, even through a block.

A redstone comparator treats certain blocks behind it as power sources and output a signal strength proportional to the block's state. The comparator may be separated from the measured block by a solid block. However, in Java Edition, if the solid block is powered to signal strength 15, then the comparator outputs 15 no matter the fullness of the container.^[1]

Containers[edit]

Minimum Items for Container Signal Strength

Containers

Total Number of Slots

3

5

9

27

54

1

Power Level

Number of Items

Music Disc

0

No music disc inserted

1

"13"

2

14

23

42

1s
60

3s
55

"cat"

3

28

46

1s
19

3s
55

7s
46

"blocks"

4

42

1s
5

1s
60

5s
51

11s
37

"chirp"

5

55

1s
28

2s
37

7s
46

15s
28

"far"

6

1s
5

1s
51

3s
14

9s
42

19s
19

"mall"

7

1s
19

2s
10

3s
55

11s
37

23s
10

"mellohi"

8

1s
32

2s
32

4s
32

13s
32

27s

"stal"

9

1s
46

2s
55

5s
10

15s
28

30s
55

"strad"

10

1s
60

3s
14

5s
51

17s
23

34s
46

"ward"

11

2s
10

3s
37

6s
28

19s
19

38s
37

"11"

12

2s
23

3s
60

7s
5

21s
14

42s
28

"wait"

13

2s
37

4s
19

7s
46

23s
10

46s
19

"Pigstep"

14

2s
51

4s
42

8s
23

25s
5

50s
10

—

15

3s

5s

9s

27s

54s

—

Using a redstone comparator to measure the state of a container will output a signal strength in proportion to how full the container is (0 for empty, 15 for full, etc.).

Containers that can be measured by a comparator include:

Furnace
Blast Furnace
Smoker
Brewing Stand
Hopper
Minecart with Hopper on top of a detector rail
Dispenser
Dropper
Chest
Trapped Chest
Minecart with Chest on top of a detector rail
Barrel
Large chest
Large trapped chest
Shulker Box (any color)

Generally speaking, the comparator output signal strength represents the average fullness of the slots, based on how many of that item form a full stack (64, 16, or 1 for non-stackable items).

The Minimum Items for Container Signal Strength table (right) shows the minimum number of 64-stackable items required to produce the different signal strengths from each type of container. Numbers followed by an "s" indicate the number of normal 64-stack equivalents ("s"), and additional items less than a stack required. For items that stack in 16 maximum (snowballs, signs, ender pearls, etc.), normal value must be divided by 4, each unity is equal to 4. Example: 3 ender pearls *4 = 12 normal stackable items. Each non-stackable item counts as one full-stack(64).

For example, to produce a signal strength of 10 from a hopper requires the equivalent of 3 full stacks plus 14 more items, or 206 items total, assuming they all stack in 64.

When a comparator measures a large chest or large trapped chest, it measures the entire large chest (54 slots), not just the half directly behind the comparator. A chest or trapped chest that cannot be opened (either because it has an opaque block, ocelot, or cat above it) always produces an output of 0 no matter how many items are in the container — shulker boxes can always be measured, even if they cannot open.

Calculating signal strength from items

When a container is empty, the output is off.

When it is not empty, the output signal strength is calculated as follows:

signal strength = floor(1 + ((sum of all slots' fullnesses) / (number of slots in container)) * 14)

fullness of a slot = (number of items in slot) / (max stack size for this type of item)

Example: 300 blocks in a dispenser (which has 9 slots), where each block stacks to a maximum of 64, produces output with a signal strength of 8:

1 + ((300 items / 64 items per slot) / 9 slots) * 14 = 8.292, floored is 8

Note that a non-stackable item is counted as a full slot (1 item in a slot, with a max stack size of 1: 1 / 1 = 1.0), and items that stack up to 16 (such as ender pearls, snowballs and eggs) are similarly considered a full slot at 16.

Calculating items from signal strength

It can be useful in redstone circuits to use containers with comparators to create signals of a specific strength. The number of items required in a container to produce a signal of desired strength is calculated as follows:

items required = max(desired signal strength, roundup((total slots in container * 64 / 14) * (desired signal strength - 1) ) )

Example: To use a furnace (which has 3 slots) to create a strength 9 signal, players need 110 items:

max(9, (3*64/14)*(9-1)) = 109.714, rounded up is 110

Miscellaneous[edit]

Comparators used to measure containers.

Some non-container blocks can also be measured by a redstone comparator:

Beehive and Bee nest

A hive or nest outputs a signal strength equal to the amount of honey in the hive/nest.

Cake

A cake outputs a signal strength relative to the amount of cake remaining. Each slice is worth 2 signal strength, with 7 total slices, for an output of 14 for a full cake.

Cauldron signal strength

Cauldron

A cauldron outputs different signal strengths depending on how much water is inside. From completely empty to completely full, the output values are 0, 1, 2, and 3. If lava is inside, the strength is always 1‌^{[upcoming: JE 1.17]} or 3‌^{[Bedrock Edition only]}

Composter signal strength

Composter

A composter outputs different signal strengths depending on the level inside. From completely empty to completely full, the output values are 0, 1, 2, 3, 4, 5, 6, 7 and 8.

Command Block

A command block stores the "success count" of the last command executed, which represents the number of times the most recently used command of this command block succeeded. A "success" is defined by the command's success conditions: if a red error message is returned in the chat, the command was not successful.

Most commands can succeed once per execution, but certain commands (such as those that accept players as arguments) can succeed multiple times, and the comparator outputs the number of times it succeeded (maximum 15 when sent to redstone dust, but in the code is able to go up to 32-bit integer limit, and can be used in contraptions with no redstone dust with those values).

A command block continues to store the success count of the last command executed until it executes its command again, thus the comparator continues to output the same signal strength even after the command block is no longer being activated (it doesn't turn off when the signal to the command block turns off).

Daylight Sensor

A Daylight Sensor outputs a signal strength that varies with the time of day (or time of night if inverted).

End Portal Frame

An end portal frame outputs a full signal of 15 if it contains an eye of ender and zero otherwise.

A comparator can measure the presence and rotation of an item frame's contents.

Item Frame

A comparator can measure the state of an item frame's contents. An item frame comparator outputs 0 if the item frame is empty, or 1 to 8 for any item depending on its rotation: 1 at initial placement, plus 1 for each 45° of rotation for a maximum of 8.

For an item frame that holds a map, a unit of rotation is 90° instead of 45°, but a comparator still outputs power levels 1 to 8. It takes two full rotations to cycle through all comparator outputs, and each orientation of the map corresponds to two output levels that differ by 4.

The comparator must be placed behind the block the item frame is attached to, facing away from the item frame. The block must be a full block, and the item frame cannot be submerged in water. Having a sign in the same block as the item frame will prevent the frame from sending a signal as well.‌^{[Java Edition only]}

Jukebox

A jukebox outputs a signal strength indicating which music disc is currently playing. See the Minimum Items for Container Signal Strength table above.

Lectern

A lectern outputs a signal strength that depends on what page the player is currently on. (e.g. a book with 15 pages powers 1 redstone level per page, or one with 5 pages emits 3 signal strength per page.)

Respawn Anchor

A respawn anchor outputs a signal strength of 0, 3, 7, 11, or 15, depending on the “charged” value.

Sculk Sensor ‌^{[upcoming: JE 1.17 & BE 1.17]}

A sculk sensor outputs a signal strength depending on the type of vibration that is detected.

Target

A Target outputs a signal strength depending on the accuracy of an arrow toward the center of the target.

Sounds[edit]

Generic[edit]

Java Edition:

Subtitle	Source	Description	Namespaced ID	Translation key	Volume	Pitch	Attenuation distance
Block broken	Blocks	Once the block has broken	`block.wood.break`	`subtitles.block.generic.break`	1.0	0.8	16
None^{[sound 1]}	Blocks	Falling on the block with fall damage	`block.wood.fall`	None^{[sound 1]}	0.5	0.75	16
Block breaking	Blocks	While the block is in the process of being broken	`block.wood.hit`	`subtitles.block.generic.hit`	0.25	0.5	16
Block placed	Blocks	When the block is placed	`block.wood.place`	`subtitles.block.generic.place`	1.0	0.8	16
Footsteps	Blocks	Walking on the block	`block.wood.step`	`subtitles.block.generic.footsteps`	0.15	1.0	16

↑ ^a ^b MC-177082

Bedrock Edition:

Sound	Source	Description	Namespaced ID	Volume	Pitch
?	Blocks	Once the block has broken	`dig.wood`	1.0	0.8
?	Blocks	Falling on the block with fall damage	`fall.wood`	0.4	1.0
?	Blocks	While the block is in the process of being broken	`hit.wood`	0.23	0.5
?	Blocks	Jumping from the block	`jump.wood`	0.12	1.0
?	Blocks	Falling on the block without fall damage	`land.wood`	0.18	1.0
?	Blocks	Walking on the block	`step.wood`	0.3	1.0
?	Blocks	When the block is placed	`use.wood`	1.0	0.8

Unique[edit]

Java Edition:

Sound	Subtitle	Source	Description	Namespaced ID	Translation key	Volume	Pitch	Attenuation distance
	Comparator clicks	Blocks	Sound played when switching between comparison and subtraction modes	`block.comparator.click`	`subtitles.block.comparator.click`	0.25	?	16

Data values[edit]

ID[edit]

Java Edition:

Name	Namespaced ID	Form	Translation key
Redstone Comparator	`comparator`	Block & Item	`block.minecraft.comparator`

Name	Namespaced ID
Block entity	`comparator`

Bedrock Edition:

Redstone Comparator	Namespaced ID	Numeric ID	Form	Translation key
Unpowered block	`unpowered_comparator`	`149`	Block	`tile.unpowered_comparator.name`
Powered block	`powered_comparator`	`150`	Block	`tile.powered_comparator.name`
Item	`comparator`	`404`	Item	`item.comparator.name`

Name	Savegame ID
Block entity	`Comparator`

Metadata[edit]

In Bedrock Edition, redstone comparators use the following data values: A redstone comparator's block data specifies its orientation, mode, and powered status.

Bits	Values
0x1 0x2	A two-bit field storing a value from 0 to 3 specifying the redstone comparator's orientation: 0: Facing north. 1: Facing east. 2: Facing south. 3: Facing west.
0x4	Set if in subtraction mode (front torch up and powered).
0x8	Set if powered (at any power level).

Block states[edit]

Java Edition:

Name	Default value	Allowed values	Description
facing	`north`	`east` `north` `south` `west`	The direction from the output side to the input side of the comparator, or the opposite from the direction the player faces while placing the comparator.
mode	`compare`	`compare` `subtract`	Specifies the current mode of the redstone comparator.
powered	`false`	`false` `true`	True if the redstone comparator is being powered.

Bedrock Edition:

Name	Default value	Allowed values	Description
direction	`0`	`0` `1` `2` `3`	The direction from the output side to the input side of the comparator, or the opposite from the direction the player faces while placing the comparator.
output_lit_bit	`0`	`0` `1`	True if the redstone comparator is being powered.
output_subtract_bit	`0`	`0` `1`	Specifies the current mode of the redstone comparator.

Block data[edit]

A redstone comparator has a block entity associated with it that holds additional data about the block.

Block entity data
- Tags common to all block entities
- OutputSignal: Represents the strength of the analog signal output of this redstone comparator.

Video[edit]

History[edit]

This section is missing information about Did MC-50242 also affect comparators?.

Please expand the section to include this information. Further details may exist on the talk page.

For a more in-depth breakdown of changes to repeater textures and models, including a set of renders for each state combination, see /Asset history

Java Edition

November 24, 2012 Jeb stated that there may be a "capacitor" in Minecraft.

December 27, 2012 Dinnerbone released pictures of the first version of the "comparator", stating it was a replacement for the "capacitor" idea that has variable, alternate inputs.

January 2, 2013 Dinnerbone released one more picture of the comparator. The picture itself showing a digital-to-analog converter, using the comparator as the main block.

1.5 13w01a Added redstone comparators.

Redstone comparators have 0 delay.

13w01b A delay of 1 game tick (¹⁄₂ redstone tick) has now been added to redstone comparators to fix bugs.

The ability to measure containers to redstone comparators has now been added.

13w02a The appearance of redstone comparators has now been changed - the top texture has changed to show quartz in the middle and the sides now use the smooth stone texture rather than the smooth stone slab side texture.

The algorithm for measuring containers has now been changed so that redstone comparators output a signal with as few as 1 item in the container.

13w02b Redstone comparators now treat large chests as a single container.

13w03a Redstone comparators now output success count of command blocks.

Redstone comparators now measure container minecarts on detector rails.

13w04a Redstone comparators now measure jukeboxes.

13w05a Redstone comparators no longer cause constant block updates. The delay has now been made consistent, and side input no longer causes a pulse output.

Block 150 (powered_comparator) is no longer used; powered state is now represented by the 8s bit on block 149 (unpowered_comparator).

13w05b Redstone comparator delay has now been changed from 1 game tick (1/2 redstone tick) to 2 game ticks (1 redstone tick).

13w09c The redstone signal strength from a redstone comparator next to a brewing stand with 3 water bottles in it is now the same as one with 3 water bottles and 1 ingredient in it.

1.6.1 13w18a Redstone comparators now measure cauldrons and end portal frames.

1.8 14w04a Redstone comparators now measure item frames.

14w10a The torches under redstone comparators have now been shortened, which has changed the underside appearance from to .

14w25a The torches on comparators are now subject to ambient occlusion.

Comparators set to subtract mode appear to be powered as well regardless of incoming power. The subtracting-only model still exists and can be achieved through /setblock.

14w25b The powered front torch when in subtraction mode is now lower.

Comparators set to subtract by hand now appear normally again.

14w28a Redstone comparators now measure cakes.

1.9

15w42a

With the addition of the blaze powder fuel slot, brewing stands now have 5 slots instead of 4. Their original comparative power values from redstone comparators are listed below:

Original values
0: 0 1: 1 2: 19 3: 37 4: 55 5: 1s 10 6: 1s 28 7: 1s 46 8: 2s 9: 2s 19 10: 2s 37 11: 2s 55 12: 3s 10 13: 3s 28 14: 3s 46 15: 4s

15w47a Redstone comparators' side inputs now take power from redstone blocks.

1.13 17w47a All 3 IDs for the redstone comparator have now been merged into one ID: comparator.

Redstone comparators now render their underside, which has changed their undersides from

to

.

Prior to The Flattening, these blocks' numeral IDs were 149 and 150, and the item's 404.

1.14 18w43a The textures of redstone comparators have now been changed.

19w02a Redstone comparators now measure lecterns.

19w03a Redstone comparators now measure composters.

19w12b Redstone comparators can now be placed on glass, ice, glowstone and sea lanterns.

1.15 19w34a Redstone comparators now measure how much honey is inside bee hives and bee nests.

1.16 20w06a The way to calculate the input signals of redstone comparators has now been changed.

20w11a The changes to the way of calculating the input signals of redstone comparators from 20w06a have now been reverted.

20w16a Redstone comparators now measure Pigstep music discs in jukeboxes.

Upcoming Java Edition

1.17 20w45a Redstone comparators now measure Lava cauldrons.

20w46a Redstone comparators now measure Powder Snow Cauldron‌s.

Pocket Edition Alpha

v0.14.0 build 1 ^[verify] Added redstone comparators.

Pocket Edition

1.0.0 alpha 0.17.0.1 Redstone comparators now measure end portal frames.

1.0.5 alpha 1.0.5.0 Redstone comparators now output success count of command blocks.

1.1.0 alpha 1.1.0.0 Redstone comparators now measure shulker boxes.

Bedrock Edition

1.2.0 beta 1.2.0.2 Redstone comparators now measure jukeboxes.

Redstone comparators now render their underside, which has changed their undersides from

to

1.10.0 beta 1.10.0.3 The textures of redstone comparators have now been changed.

1.11.0 beta 1.11.0.1 Redstone comparators now measure smokers, blast furnaces, lecterns and composters.

Legacy Console Edition

TU19 CU7 1.12 Patch 1 1.0.1 ^[verify] Added redstone comparators.

TU31 CU19 1.22 Patch 3 Redstone comparators can now measure item frames.

1.90 ^[verify] The textures of redstone comparators have now been changed.

New Nintendo 3DS Edition

0.1.0 ^[verify] Added redstone comparators.