Quick Answer
In Rust, a building block with no Tool Cupboard decays from full health to destroyed over a fixed time — Twig 1 hour, Wood 3 hours, Stone 5 hours, Sheet Metal 8 hours and Armoured (HQM) 12 hours — and the time left is proportional to health, so a stone wall at 50% HP has about 2.5 hours. A stocked Tool Cupboard stops decay entirely by paying a daily upkeep of 10–33.3% of your base's build cost, rising with the number of building blocks.
Rust Decay Times by Building Tier
When a building block is not protected by a stocked Tool Cupboard (TC), it takes decay damage until it is destroyed. The time from full health to gone is fixed for each tier, and damage is steady — so at half health a block has half the time left. That is exactly what this Rust decay calculator works out.
| Tier | Block max HP | Decay time (full HP) | Damage rate |
|---|---|---|---|
| Twig | 10 | 1 hour | ~10 HP/hour |
| Wood | 250 | 3 hours | ~83 HP/hour |
| Stone | 500 | 5 hours | 100 HP/hour |
| Sheet Metal | 1,000 | 8 hours | 125 HP/hour |
| Armoured (HQM) | 2,000 | 12 hours | ~167 HP/hour |
A Sheet Metal wall at 400 / 1000 HP has 8 h × (400 ÷ 1000) = 3.2 hours before it is destroyed.
Tier hit points come from the Rust wiki’s Building page, which states 10, 250, 500 and 2,000 for Twig, Wood, Stone and Armoured. It gives no figure for Sheet Metal, so the 1,000 used here is the in-game value.
How to Use the Rust Decay Calculator
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Choose Decay time or Upkeep cost
Use Decay time to see how long a block lasts, or Upkeep cost to see what your Tool Cupboard needs each day.
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Decay mode: pick the material and health
Select Twig, Wood, Stone, Sheet Metal or Armoured, then enter the current health. Leave it at 100% for a fresh block, or switch the picker to HP and type the exact number you see when you hit it with a hammer.
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Upkeep mode: enter build cost and block count
Type your base’s total build cost in wood, stone, metal or HQM (the Tool Cupboard shows these totals) and how many building blocks it has. The tool returns the daily drain per material and the effective tax rate.
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Read the result and plan the restock
Decay mode shows the time left and when the block is destroyed; Upkeep mode shows the daily cost and, if you enter your TC stockpile, how many days the base stays protected.
Decay Time Examples
Every row is reproducible in the calculator above — the time left is just the tier decay time scaled by the health fraction:
| Tier | Health | Working | Time until destroyed |
|---|---|---|---|
| Stone | 100% | 5 h × 1.00 | 5 h 0 m |
| Stone | 250 / 500 HP | 5 h × 0.50 | 2 h 30 m |
| Wood | 100% | 3 h × 1.00 | 3 h 0 m |
| Sheet Metal | 400 / 1000 HP | 8 h × 0.40 | 3 h 12 m |
| Armoured | 100% | 12 h × 1.00 | 12 h 0 m |
Rust Upkeep: How the Tool Cupboard Cost Works
A Tool Cupboard stops decay by paying a daily upkeep — a fraction of what your base cost to build, taken from the materials loaded in the TC. The catch: the fraction rises with the number of building blocks, so bigger bases pay a higher percentage per block. On vanilla servers the brackets are:
| Building blocks | Upkeep rate on those blocks |
|---|---|
| 1 – 15 | 10% |
| 16 – 50 | 15% |
| 51 – 125 | 20% |
| 126 and up | 33.3% |
The rates are averaged across all your blocks, so a 24-block base pays (15 × 10% + 9 × 15%) ÷ 24 ≈ 11.9% of its build cost per day. A base that costs 3,000 stone would drain about 356 stone every 24 hours.
On these numbers: Facepunch publishes no upkeep table, so the bracket boundaries (15 / 50 / 125) and their rates are the in-game vanilla values rather than a documented figure. The closest published source, CorrosionHour, states only that upkeep starts at 10%, begins rising past 16 building blocks, and can reach 30%.
