Spawner production is calculated, not simulated: a managed spawner stores how many mobs its tank holds and works out the current fill from the time passed. It keeps producing while you are offline and while its island is unloaded.
Formula#
output per hour = units x 240 x level multiplier x boosts
tank capacity = units x 240 x level multiplier x tank hours (boosts do not enlarge the tank)
The fill grows linearly until it reaches the capacity. A full tank stops producing and the hologram turns red ("Tank full") until you reap.
All 17 mobs share the same base rate of 240 mobs per unit per hour. Mobs differ in drops, price and unlock requirements, not in speed.
| Level | Multiplier | Mobs per hour per unit | Tank capacity per unit (8 hours) | Tank capacity per unit (48 hours) |
|---|---|---|---|---|
| I | x1 | 240 | 1,920 | 11,520 |
| II | x1.2 | 288 | 2,304 | 13,824 |
| III | x1.4 | 336 | 2,688 | 16,128 |
| IV | x1.6 | 384 | 3,072 | 18,432 |
| V | x1.8 | 432 | 3,456 | 20,736 |
| VI | x2 | 480 | 3,840 | 23,040 |
| VII | x2.25 | 540 | 4,320 | 25,920 |
| VIII | x2.5 | 600 | 4,800 | 28,800 |
| IX | x2.75 | 660 | 5,280 | 31,680 |
| X | x3 | 720 | 5,760 | 34,560 |
Example: a spawner with 10 sheep units at level I, base tank: 10 x 240 = 2,400 mobs per hour, filling its tank of 19,200 mobs in 8 hours.
Boosts#
The Island Booster Beacon boosts managed spawners within its radius (Island Booster Beacon). The boost multiplies the output rate only. Offline production uses the unboosted rate, because beacons only work in a loaded world.
Hologram and menu#
Each spawner shows a hologram above its block with the mob name, units and tank fill. When the tank is full it switches to a red Tank full line. Right-click the spawner for the menu, which shows:
| Entry | Meaning |
|---|---|
| Spawner info | Mob, level, units, production per hour, level multiplier and boosts, tank fill and capacity, tank size in hours. |
| Upgrades | Next level, next tank size and next automation yield; opens Spawner Upgrades. |
| Next unit | Units your island owns, free re-placements, and the fee of the next new unit. |
| Storage | Drops that did not fit your inventory; click to take everything. |
| How to harvest | Reminder of the harvest rules (Reaping Spawners). |
| Picking this spawner up | Warns that the tank is lost when you break the spawner. |
Display mob#
Above each spawner a silent mob of its type stands as a target. It cannot be hurt by fire, lava, falls, suffocation or other mobs, cannot be named, sheared, leashed or traded with, and never drops loot by itself. It only exists so that you can hit it to reap.