Minecraft Mob Farm Calculator
Editions: Java (Bedrock differs — see FAQ) · Verified: Java 26.3 · 2026-09-16 · Updated 2026-09-16
A hostile mob farm lives or dies by three spheres around the player: nothing spawns inside 24 blocks, nothing spawns or survives outside 128, and past 32 a despawn timer starts. Enter your AFK spot and platform heights, and this checks all three.
The worked example
AFK at Y=200 with platforms directly below at Y=170 puts the farm exactly 30 blocks away: outside the 24-block no-spawn sphere, comfortably inside the 128 cap, and inside 32 so the despawn timer never arms. With the ground at Y=63, the vertical offset is 137 — beyond 128 — so the entire surface is out of spawn range and needs no lighting at all. Lower the AFK spot to Y=163 and the offset to the ground becomes 100: now the sphere cuts the surface in a circle of radius just under 80 blocks that has to be spawn-proofed or accepted as competition.
The three radii
| Sphere | Radius | What happens there |
|---|---|---|
| No-spawn | 24 | No hostile spawns this close to a player (or the world spawn point) |
| Despawn timer | 32 | Beyond this for 30+ seconds: 1-in-800 despawn roll per game tick |
| Hard cap | 128 | No spawns beyond it; mobs past it despawn instantly |
Java rules, spherical distances; sources in the farm spheres guide.
Questions builders actually ask
Why does my mob farm stop working when I stand next to it?
Hostile mobs cannot spawn within a 24-block spherical radius of any player, so standing on top of a farm switches its spawning spaces off. AFK spots are placed 24 or more blocks from the platforms on purpose.
How far can my farm be from the AFK spot?
In Java, spawning is capped to a 128-block radius sphere around the player, and mobs beyond 128 blocks despawn instantly. The working band is therefore 24 to 128 blocks; past 32 blocks the random-despawn timer arms, so mobs should be killed or collected within about 30 seconds.
Why do farms get built over oceans or high in the sky?
The 128-block sphere is the whole spawning world while you AFK. If the ground below is more than 128 blocks away, or holds no spawnable spaces because it is water, the farm's platforms are the only place mobs can appear — which is the entire trick.
Does this tool apply to Bedrock Edition?
The tool models Java. Bedrock spawns in a shell 24 to 44 blocks from the player at simulation distance 4, and 24 to 128 at simulation distance 6 or higher, so its numbers move with your settings. The 24-block inner rule is common to both editions.