Comparator Guide

Quick answer

• A Comparator reads how full a container is and turns it into a signal from 1 to 15.
• Click it to switch between compare mode and subtract mode.
• It also reads cakes, composters, item frames, jukeboxes and more.

Comparators are the redstone part that "looks inside" blocks. They're how auto smelters know a chest is full and how item sorters work.

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Crafting

You need Nether quartz from the Nether, so comparators come a little later than other redstone parts.

The two modes

Reading containers

Put a comparator facing away from a chest, hopper, barrel or furnace. Any item inside gives at least 1. A full container gives 15.

The signal goes up with how full the slots are, not how many items there are. So a chest of tools fills up the signal far faster than a chest of dirt.

Other blocks it reads

Block	Signal
Cake	2 per slice left, 14 when full
Composter	0 to 8 by fill level
Cauldron	0 to 3 by fill level
Item frame	1 to 8 by rotation
Jukebox	Depends on the disc
End portal frame	15 with an eye of ender
Beehive	0 to 5 by honey level
Respawn anchor	0, 3, 7, 11 or 15 by charge
Lectern	Higher the further through the book

Cheat sheet

• 3 redstone torches, 1 quartz, 3 stone
• Front torch off: compare. On: subtract
• Full container gives 15
• Hopper: 23 items for signal 2

Stack & Shulker CalculatorConvert Minecraft items into stacks, shulker boxes and chests→