How this instrument works
This is about Rust, the survival video game, and its base-building decay mechanic — not metal corrosion in the chemistry sense. In Rust, any structure that isn't protected by a Tool Cupboard with sufficient stored resources for upkeep loses health steadily over time until it's fully destroyed, a deliberate game-design mechanic that prevents the map from filling up permanently with abandoned bases. Each building material tier decays at its own fixed base rate, defined by the game's default server settings.
The five tiers, from flimsiest to toughest, take very different amounts of time to fully decay from 100% health with no upkeep: Twig just 1 hour, Wood 3 hours, Stone 5 hours, Sheet Metal 8 hours, and Armored 12 hours. That twelve-fold spread between Twig and Armored reflects both the much higher resource cost of building in tougher materials and a game-balance choice to make flimsy starter structures disappear quickly while a well-invested base holds up far longer without maintenance.
Decay time scales linearly with remaining health — a structure at 50% health has exactly half its base decay time left, not some more complicated curve. That's a genuinely useful, memorable rule: know a tier's 100%-health decay time and you can estimate remaining time at any health percentage with simple proportional math, without needing separate figures for every possible health level.
- Select Building material — Twig, Wood, Stone, Sheet Metal, or Armored, the five structural tiers in Rust.
- Enter Current health (%) — the structure's current health as a percentage of full health.
- Read Time until fully decayed — hours remaining before this structure decays away completely, assuming no upkeep is added.
Worked example — a Stone wall losing upkeep
A Stone structure at 100% health, with no upkeep in its Tool Cupboard, takes exactly 5 hours to fully decay — Stone's official base decay time. If that same wall is instead found at 50% health, the linear relationship gives 5 x (50/100) = 2.5 hours remaining, a concrete, independently corroborated data point (a Stone wall at half health having roughly two and a half hours left) that's consistent across the game's own wiki and multiple community decay-calculator sites.
Comparing tiers at full health shows the design intent clearly: Twig decays in just 1 hour, by design, so throwaway starter structures don't linger on the map; Armored takes 12 hours, twelve times longer, reflecting both its much higher build cost and its role as a serious, defensible base material. A Sheet Metal structure (8-hour base) at 25% health has 8 x (25/100) = 2.0 hours left — the same simple proportional math applies to every tier.
Questions
What stops a structure from decaying in Rust?
A Tool Cupboard (TC) placed within range of the structure, stocked with the resource type that structure is built from (wood, stone, metal fragments, or high-quality metal, depending on tier). As long as the TC holds enough of the matching resource, upkeep is deducted from it each cycle and the structure's health stays full; once that resource runs out, decay begins at the tier's normal rate. This calculator models the no-upkeep, actively-decaying case.
Does decay time scale linearly with health, or is it more complicated?
It's linear — a structure at 50% health has exactly half its tier's base decay time remaining, at 25% health exactly a quarter, and so on. This is confirmed both by the game's own wiki and independently by multiple community decay calculators, all citing the same concrete example: a Stone wall at 50% health has about 2.5 hours left, precisely half of Stone's 5-hour base decay time.
Why does Twig decay so much faster than other tiers?
By deliberate game design. Twig is the cheapest, weakest building tier — often placed temporarily while a base is being built up — and its fast 1-hour decay ensures abandoned or incomplete twig structures clear off the map quickly rather than cluttering it indefinitely. It's the fastest of all five tiers by a wide margin.
What decaytickrate does this calculator assume?
The game's default server setting, decaytickrate=300, which is what most official and popular community servers run. Some private or modded servers configure a different decay tick rate, which changes actual in-game decay speed proportionally — on a server with a custom decay rate, treat this calculator's hours as a baseline to scale by that server's specific multiplier rather than an exact prediction.
Is this the same decay mechanic as real-world metal corrosion?
No — despite the shared word "decay," this is entirely a video-game mechanic from Rust (Facepunch Studios), governed by fixed server-defined base decay times per building tier, not a model of real rust, oxidation, or material degradation. Nothing here applies to actual metal, wood, or building-material corrosion outside the game.