The Three Spheres Around Every AFK Spot

Verified: Java 26.3 · 2026-09-16 · Java rules; Bedrock differences noted · Updated 2026-09-16

Every hostile mob farm that works is solving the same geometry problem, whether its builder knows it or not: put the platforms inside one sphere, the player outside another, and the rest of the world outside a third. The mob farm calculator does the arithmetic; this guide explains where the numbers come from.

Sphere one: 24 blocks of quiet

Hostile mobs cannot spawn within a 24-block spherical radius of any player — or of the world spawn point, a detail that has quietly killed many a farm built at spawn for a farm-hub base. The distance is three-dimensional and unforgiving: stand on top of your spawning platforms and you switch them off. This is why every farm design puts the AFK spot a deliberate distance away, and why "it works when my friend stands there but not when I do" is almost always someone standing two blocks too close.

Sphere two: 128 blocks of world

Spawning in Java is capped to a 128-block radius sphere centered on the player, and hostile mobs that end up farther than 128 blocks from the nearest player despawn instantly. Both halves matter. The cap means your farm must sit inside the sphere to produce anything; the instant despawn means everything outside it stops existing, which is a feature — while you AFK inside the sphere, the 128-block ball is the entire spawnable world. The game also only attempts spawns in chunks with a player within 128 blocks horizontally of the chunk center, which is the same idea applied per chunk.

This is the whole reason classic farm designs float over oceans or hang in the sky. Every spawnable cave and every dark forest floor inside your sphere competes with the farm for the mob cap — the game's limit on how many hostiles it keeps alive around you. Push the AFK spot high enough that the ground leaves the sphere entirely and the competition simply is not there: the farm's platforms become the only valid spawning spaces in existence, and rates jump accordingly.

Sphere three: the 32-block timer

Between the other two radii sits a subtler one. A mob that is more than 32 blocks from every player for more than 30 seconds starts rolling a 1-in-800 despawn chance every game tick — about a coin flip every half minute of lingering. Mobs within 32 blocks never roll it. For farm design this sets the collection deadline: if your platforms are past 32 blocks (most are), the mobs must fall, flush, or die within roughly 30 seconds of spawning, or a measurable fraction of them will evaporate mid-journey. Water streams and drop shafts are not decoration; they are the timer being beaten.

The height trick, quantified

The calculator's third output is the one that saves the most torches. The 128-sphere meets a horizontal plane at vertical offset dy in a circle of radius the square root of 128² − dy² — and if the offset exceeds 128, it misses the plane entirely. AFK at Y=200 over ground at Y=63 and the offset is 137: no part of the surface is in range, and not one torch is needed. Drop the AFK spot to Y=163 and the offset becomes 100, which cuts the surface in a circle of radius just under 80 blocks — some 20,000 square blocks of cave-riddled ground now competing with your farm unless you light it. Thirty-seven blocks of AFK height is the difference between zero perimeter work and a weekend of it. That arithmetic, not platform design, is usually what separates a good farm spot from a bad one.

Bedrock plays by different shells

The calculator models Java. Bedrock spawns hostiles in a shell between 24 and 44 blocks from the player at simulation distance 4, and between 24 and 128 at simulation distance 6 or higher — the working band moves with a settings slider, and despawn behavior is tied to those same ranges and the simulation edge rather than a single clean number. The 24-block inner sphere is common ground. If you build on Bedrock, treat this guide's inner-radius logic as portable, check your simulation distance before trusting any outer-radius figure, and expect platform heights tuned for Java sky farms to need rework.

What this page deliberately leaves out

Mob cap arithmetic (the cap's exact size and per-category weighting deserve their own verification pass), pack-spawn mechanics, per-mob spawn weights, light-source edge cases on the platforms themselves, and spawn-attempt frequency. None of them changes the three radii, and the radii are what farm placement lives or dies by.

Sources

The 24-block spherical no-spawn rule, the 128-block spawning sphere, the chunk-center condition, and the Bedrock simulation-distance shells are stated on the Minecraft Wiki's mob spawning page; the instant-despawn rule and the 32-block, 30-second, 1-in-800 random despawn are on its despawning coverage (minecraft.wiki/w/Mob_spawning and /w/Mob_spawning#Despawning). Those two pages are the whole of the sourcing here. All checked 2026-09-01 against Java 26.2.