Rust Decay Calculator: Time to Decay, HP Loss & TC Upkeep
Enter your building's material tier and current health percentage to see how long it will take to fully decay without Tool Cupboard upkeep. Toggle sheltered mode for structures under a roof, and use the base-upkeep section to calculate how many resources your TC needs per day based on your total piece count. Results update instantly as you type.
Formula
Worked example
A Stone wall at 60% HP outdoors: base decay = 5 h, so 5 h x 0.60 = 3 h remaining. It loses 500 HP / 5 h = 100 HP per hour. A 40-piece stone base needs 40 x 10 = 400 stone per day from the TC.
How decay works in Rust
Every building piece in Rust has a maximum HP tied to its material tier: Twig has just 10 HP, Wood 250 HP, Stone 500 HP, Sheet Metal 1,000 HP, and Armored 2,000 HP. When no Tool Cupboard is present, or when the TC runs out of resources, pieces start losing HP at a fixed rate. The rate depends entirely on the tier: at full health, Twig lasts 1 hour, Wood 3 hours, Stone 5 hours, Sheet Metal 8 hours, and Armored 12 hours outdoors.
Shelter matters. A piece that is fully covered by a roof decays more slowly: Wood lasts 6 hours, Stone 8 hours, Sheet Metal 12 hours, and Armored 16 hours. Twig is an exception - it always decays in 1 hour regardless of shelter or TC stock, because it is an intentional anti-griefing mechanic designed to clear abandoned twig frames quickly.
HP-based scaling: if a piece is already damaged, it has less time remaining. A Stone wall at 50% HP has 2.5 hours left outdoors, not 5. The formula is simply base decay time multiplied by the current HP fraction.
How to use this calculator
Select your building material from the dropdown - choose the tier of the specific piece you are worried about, not the whole base. Enter the current HP percentage. If the piece is under a roof, switch the sheltered toggle to "Yes" to get the slower decay rate. The decay time, HP loss per hour, and daily TC upkeep cost all update instantly.
The "Total Pieces in TC Range" field estimates your daily upkeep: enter the total number of building blocks (walls, floors, foundations, doorframes, ceilings, roofs) within 40 metres of your TC. Placed items such as sleeping bags and boxes do not contribute to upkeep costs. If your base uses mixed materials, run the calculator once per tier and sum the daily costs.
The decay chart shows how HP drops over time from the current health level to zero, so you can plan exactly when to return and refill the TC.
Tool Cupboard upkeep: rates and brackets
The TC draws resources every 24 in-game hours. The drain rate scales with how full the TC is:
- Above 50% capacity: 10% of daily construction cost - the cheap bracket.
- Below 50% capacity: 30% of daily construction cost - triple the drain rate.
This calculator uses the 10% rate (TC above half full), which is the rate you want to maintain. The practical lesson: keep your TC topped up above the halfway point, and your costs stay predictable. Let it drop below half and you will burn through resources three times faster.
When a TC is raided and destroyed, it automatically consumes up to 24 hours of upkeep material to delay decay during the raid, giving defenders a grace period.
Daily upkeep cost per piece by tier: Wood - 5 wood, Stone - 10 stone, Sheet Metal - 5 metal fragments, Armored - 1 HQM. Twig pieces have no TC upkeep because no TC covers twig.
Planning your base around decay
The most common mistake in Rust is letting a TC empty overnight. Here is a practical planning approach:
- Count your pieces. Use this calculator's upkeep field, or count walls, floors, and foundations in your build. A compact 2x2 two-floor stone base typically has around 40-60 pieces.
- Calculate weekly stock. Multiply daily upkeep by 7 for a weekly stockpile. A 50-piece stone base needs 50 x 10 = 500 stone/day, or 3,500 stone per week.
- Mix tiers wisely. Armored walls cost only 1 HQM per piece per day, making them very cheap to maintain relative to their HP. A mix of armored outer walls and stone inner structure can be more cost-efficient than full stone.
- Shelter inner rooms. Building a roof over storage areas means inner walls decay at the sheltered rate, doubling or more the survival window if the TC empties unexpectedly.
Rust Building Tier Decay Reference
| Material Tier | Max HP | Outdoor Decay | Sheltered Decay | Upkeep Resource | Cost per Piece/Day |
|---|---|---|---|---|---|
| Twig | 10 | 1 h | 1 h | N/A (no TC) | 0 |
| Wood | 250 | 3 h | 6 h | Wood | 5 |
| Stone | 500 | 5 h | 8 h | Stone | 10 |
| Sheet Metal | 1000 | 8 h | 12 h | Metal Fragments | 5 |
| Armored | 2000 | 12 h | 16 h | HQM | 1 |
Base decay times and daily TC upkeep costs per piece on a vanilla Facepunch server (decaytickrate 300). Sheltered times apply to pieces fully covered by a roof.
Frequently asked questions
How long does a stone wall take to decay in Rust?
A stone wall at 100% HP decays in 5 hours outdoors and 8 hours under a roof when the Tool Cupboard has no upkeep. At 50% HP those times halve to 2.5 hours outdoors and 4 hours sheltered. Keep your TC stocked with stone to stop decay entirely.
Does decay still happen if my TC has resources?
No. As long as your Tool Cupboard contains the correct materials and is not empty, building pieces in its 40-metre radius do not take decay damage at all. Decay only begins once the TC runs out of a particular material, and only affects pieces made of that material.
Why does twig always decay so fast?
Twig decay to 1 hour is intentional. Facepunch designed it so that cheap twig scaffolding and griefing frames auto-clean themselves quickly. No Tool Cupboard can prevent twig decay - you must upgrade the piece to Wood or higher if you want TC protection.
What is the TC upkeep drain rate?
The TC drains roughly 10% of your total building construction cost per real-time day when the cupboard is above 50% capacity. If it drops below 50%, the drain rate rises to 30% - three times higher. This calculator uses the 10% rate. The key takeaway: refill your TC before it reaches the halfway point.
Does being sheltered (under a roof) reduce decay?
Yes. Pieces fully covered by a ceiling or roof decay significantly more slowly. Wood goes from 3 hours to 6 hours, Stone from 5 to 8 hours, Sheet Metal from 8 to 12 hours, and Armored from 12 to 16 hours. Twig is not affected by shelter.
How do I calculate daily TC upkeep for a mixed-material base?
Run the calculator separately for each material tier, entering the number of pieces of that tier. Then add the daily costs together. For example, 30 stone walls (30 x 10 = 300 stone) plus 10 sheet metal walls (10 x 5 = 50 metal fragments) requires 300 stone and 50 metal fragments per day.
What happens when the TC is destroyed during a raid?
When raiders destroy your Tool Cupboard, it auto-consumes up to 24 hours of upkeep resources before triggering decay. This gives you a window to retake your base or place a new TC. After that 24-hour buffer, exposed pieces begin losing HP at the normal decay rate.