Minecraft Comparator Calculator
Editions: Java + Bedrock (fullness math shared — reading quirks differ, see FAQ) · Verified: Java 26.3 / Bedrock 26.50 · 2026-09-16 · Updated 2026-09-16
A comparator reading a container reports how full it is, not how much is in it. Put a load in below and get the signal strength it produces, the exact count that reaches any level from 1 to 15, and the two output modes side by side. Every threshold here reproduces the wiki's own minimum-items table, cell for cell, in the test suite.
Items to signal strength
Signal strength to items
The other direction, for when a circuit needs one exact level. The table below is for the container selected above.
Comparison and subtraction modes
The other half of the block. Signal strengths run 0 to 15; the front torch decides which rule applies.
The worked example
A single chest is 27 slots at 64 each, or 1,728 in full-stack-equivalent, so 864 cobblestone fills exactly half of it — and half of 14 is 7. Add the 1 that every non-empty container starts with and the comparator reads 8. Getting to 9 takes 988 in total, which is 124 more. The first item is the cheap one: a single cobblestone in that same chest already reads 1, and the remaining fourteen levels each cost about 123.4 items. That is the whole shape of the curve, and it is why storage-monitor circuits count levels, not items.
The mixed case works the same way once everything is converted to full-stack-equivalent. Three minecarts and 14 dirt in a hopper come to 3 × 64 + 14 = 206, and 206 in a five-slot container reads 10 — the wiki's own worked example, asserted in this tool's tests along with all 90 cells of its threshold table.
Blocks that use a different rule
Not everything a comparator can read is a container. These blocks report a state instead of a fullness, so the calculator above does not apply to them.
| Block | What the comparator outputs |
|---|---|
| Composter | the compost level, 0 to 8 |
| Cake | 2 per remaining slice — 7 slices, so 14 for a whole cake |
| Cauldron | the water or powder snow level, 0 to 3; lava always reads 3 |
| Chiseled bookshelf | the last slot placed into or taken from, 1 to 6, and 0 until one is |
| Lectern | floor(1 + ((page − 1) ÷ (pages − 1)) × 14) — a 15-page book reads its page number |
| Respawn anchor | 0, 3, 7, 11 or 15 by charge level |
| Crafter | the number of slots filled or disabled, 0 to 9 — not how full they are |
| End portal frame | 15 with an eye of ender in it, 0 without |
| Item frame | 0 when empty, then 1 to 8, one step per 45° of rotation |
Formulas, thresholds and the block rules above come from the Minecraft Wiki's comparator page (minecraft.wiki/w/Redstone_Comparator), re-checked 2026-09-09. Every threshold this page prints was also checked against the comparator signal calculator at minecraftmaps.com/tools/comparator-signal-calculator, which matches on all 90 cells. The comparator guide shows the working.
Questions builders actually ask
How does a comparator read a container?
It measures average fullness, not item count. Each slot contributes the items it holds divided by that item's maximum stack size, those fractions are averaged over every slot in the container, and the result is scaled: an empty container reads 0, anything else reads floor(1 + average fullness x 14). A chest holding one item and a chest holding 123 both read 1.
Does it matter how the items are spread between slots?
No. Because the per-slot fractions are added together before they are averaged, only the total matters. Twenty-seven slots holding 32 cobblestone each, or thirteen full stacks and one half stack, both come to 864 full-stack-equivalent in a chest and both read 8.
Why does one minecart read so high?
An unstackable item fills a whole slot on its own, so it counts as a full stack. One minecart in a hopper reads 3, the same as 64 cobblestone there, and one minecart in a decorated pot reads 15. Items that stack to 16, such as snowballs, signs and ender pearls, each count four times as much as a 64-stackable item.
Do Java and Bedrock read containers differently?
The fullness formula is documented without an edition split, and this tool models it for both. The reading quirks around it do differ. In Java a chest that cannot open, because a solid block or a sitting cat is above it, reads 0 however full it is, and a comparator reading through an intervening block that is itself powered to 15 outputs 15 regardless of the container. Bedrock treats several non-conductive blocks, including chains and pistons, as comparator-conducting.
Which blocks ignore the fullness formula?
Several, and they are listed in the reference table on this page. A composter reports its compost level 0 to 8, a cake 2 per remaining slice, a cauldron its fill level 0 to 3, a chiseled bookshelf the last slot touched, and a crafter the number of slots filled or disabled rather than how full they are. Feeding those into a fullness calculator gives the wrong answer.