How this calculator works
Rust building blocks need upkeep, paid from a tool cupboard. When the cupboard has no resources of the right kind, blocks of that material begin to lose health. The loss is treated here as linear from full health to zero over the material decay window, so a stone block at half health has about half its window left. Outer parts of a base decay before the core, which is why a base can look intact outside while the inside is already gone. The server setting decay.scale stretches or shortens every window: 0.5 doubles the time and 2 halves it.
Formula
full decay time = material full-decay hours / decay scale. Time until destroyed = current health fraction x full decay time. Health after elapsed time = max(0, 1 - elapsed / full decay time). Hit points left = health fraction x material maximum hit points. Decay rate (HP per hour) = maximum hit points / full decay time.
Worked example
A stone block at 50 percent health on a vanilla server has 2.5 hours left, because stone takes about 5 hours to decay from full health. It holds 250 of its 500 hit points, and the decay rate is 500 / 5 = 100 HP per hour. A twig block at full health on the same server has about 1 hour left, and 10 HP in total. On a server with decay.scale 0.5, both windows double.
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Frequently asked questions
When does decay actually start?
Only when the tool cupboard has no upkeep of the material that a block needs, and only for blocks of that material. A stocked cupboard prevents decay entirely. The calculator starts its clock at the moment decay begins, so add the time the upkeep will last if you are planning from now.
Are these decay times official?
The upkeep mechanic comes from Facepunch Devblog 189, but Facepunch does not publish a current table of decay windows. The values used here are the ones the Rust community reference sites report for the live game in August 2026: about 1, 3, 5, 8 and 12 hours for twig, wood, stone, sheet metal and armoured. Older sources still quote shorter wood and stone windows from before the balance changed.
Why does my server decay differently?
Server owners can change decay.scale and can install plugins that alter upkeep or replace decay entirely. Enter the server scale to match the setting. If a plugin changes the material rates themselves, the calculator cannot know the new window, and you should use the server documentation or test one block.
Is decay really linear?
In the game it is a gradual loss of health over time, and this page models it as linear across the material window. Server ticks, partial upkeep and damage from other sources can make a real block fall earlier. Treat the result as a planning estimate, not a countdown to the second.
Which parts decay first?
Outer structures decay before the core, so a base loses its exposed walls and roofs before the inner rooms. That is separate from the material window: the calculator tells you how long one block of a given material lasts once its health starts dropping, not the order in which the game picks blocks.