Rust Decay Calculator - Twig to Armoured

The rust decay calculator is a single-form timer that turns a Rust game material and the current hit-point percentage of a structure into the matching time to full decay in hours, minutes, and seconds. It is built for the moment a player is about to log off, raid a neighbour, or plan a wipe and wants to know how long a building will hold up before upkeep runs out.

• • Tool Cupboard upkeep planning: Compare a material's decay time against the 24-hour Tool Cupboard upkeep cycle to know when to refill the cupboard.
• • Raid prep and base re-build: Time how long a hostile structure will stay standing after a raid to decide whether to repair, re-deploy, or move.
• • Damage assessment: Convert a partly damaged building's HP bar into a countdown so a corner does not silently disappear overnight.
• • Server-rule comparison: Cross-check the default Facepunch decay durations against a modded server's decay.tick or decay.duration_* overrides.

Every player-built structure in Rust has two decay numbers: the material tier and the current health bar. The form reads both numbers and returns the time until the structure is fully decayed under the default Facepunch convars.

The Tool Cupboard side of decay is really an inventory replenishment problem, and the Reorder Point Calculator applies the same lead-time and restock thinking to the resources you keep inside the cupboard.

Two short formulas do the whole job behind the form: look up the base decay time for the material, then divide that base time by the current HP expressed as a decimal.

• baseTime_hours: Default decay duration for the chosen material tier: Twig 1h, Wood 3h, Stone 5h, Sheet Metal 8h, Armoured 12h.
• currentHP_percent: Current health bar of the structure, expressed as a percentage from 0.01 to 100.
• decayTime_hours: Total hours the structure will take to fully decay from the current HP at the default 300-second decaytickrate.

The form follows the Omni Rust decay formula, so the displayed hours equal the base decay time divided by the current HP expressed as a decimal. A 100% HP wood foundation reads 3 hours, a 50% HP wood wall reads 6 hours, and the base time itself comes from the Facepunch convars documented below.

According to the Corrosion Hour RUST Decay Upkeep Variable guide, the default decay.duration_twig / wood / stone / metal / toptier convars are 1h, 3h, 5h, 8h, and 12h, and the decay.upkeep_period_minutes convar is 1440 minutes (24 hours).

Once the result is on screen, the Time Saved/Wasted Calculator turns that decay duration into hours and minutes so you can size the upkeep window against a 24-hour Tool Cupboard cycle.

Four ideas make the form predictable: the material base-time table, the percentage-HP formula direction, the Tool Cupboard upkeep cycle, and the default decaytickrate.

These four concepts explain why the form only needs two inputs. The material picks the base time, the HP% divides that base time per the Omni formula, and the Tool Cupboard or decaytickrate changes only when the server admin overrides the default convars, so the form is a small surface area on purpose.

The same single-rate duration pattern shows up in workload timers, so the 3D Render Time Calculator applies a base duration divided by a remaining-fraction ratio to estimate how long a partial render job still has left.

Pick a material, type the current HP, and read the decay time in the panel below. The numbers update on every keystroke so the timer stays live as you tune the inputs.

1. 1 Choose the material tier: Open the Material drop-down and pick Twig, Wood, Stone, Sheet Metal, or Armoured to match the structure you are timing.
2. 2 Enter the current HP: Type the current health percentage shown in the Rust building HUD. The field clamps to 0.01% so a 0 HP building does not divide by zero.
3. 3 Read the hours value: The first row of the result panel is the decay time in hours, the same unit the Facepunch decay.duration_* convars use.
4. 4 Check the minutes and seconds: Use the minutes and seconds rows to match the timer against the 300-second default decaytickrate or the 1440-minute Tool Cupboard upkeep period.
5. 5 Confirm the material echo: The Material Tier row repeats the chosen material so you can be sure the form used the right base time before you plan around the result.

If a 50% HP wood wall is on a 3x wipe server and you are heading offline for the night, type material=Wood and HP=50. The result panel returns 6 hours, which is the 3-hour wood base time divided by 0.5. That is shorter than the 24-hour Tool Cupboard upkeep period, so the wall will start losing a layer before the cupboard refreshes, and you know to refill the cupboard before the timer hits zero.

Using the timer removes the manual lookup of each material's base time and the manual divide-by-HP arithmetic, so the result can be matched to a 24-hour Tool Cupboard cycle without a spreadsheet.

• • Single source of base times: All five Facepunch default decay.duration_* values are baked into one drop-down, so the form never makes you flip between a wiki and a server.cfg.
• • Live damage adjustment: Type the post-raid HP% and the timer updates immediately, so the result can show how much longer a partly destroyed wall still has left.
• • Tool Cupboard overlap check: The minutes row makes it easy to compare the displayed decay time against the 1440-minute upkeep period and see whether a refill is needed.
• • Multi-mode upkeep support: The same divide-by-decimal relationship works for deployable timers and vehicle decay, so the form covers the full set of player-built structures that lose HP over time.
• • Resets in one click: The Reset button restores Wood at 100% HP so the form always opens back to the standard 3-hour wood baseline for a quick sanity check.

The strongest case for the timer is removing the divide-by-HP slip that happens when a 50% HP wall is silently read as a 100% HP wall. The form takes both numbers, so the material and the HP bar are not lost between the in-game HUD and the result panel.

When a raid leaves the base half-decayed and you are weighing repair against a fresh build, the Is It Worth It? Calculator compares the resource cost of refilling the Tool Cupboard against starting a new base.

Three things decide what the form displays: the chosen material, the HP% you type, and the assumption that the server is using the default Facepunch decay convars.

• • The form does not model the inside-out decay direction (it treats the whole structure as one timer rather than a stack of layers), so the displayed time is a single total duration, not a per-layer countdown.
• • The form does not include the Tool Cupboard tax brackets from Building 3.0. The 0% HP case is clamped to 0.01% so the divisor never reaches zero, a safety floor rather than a realistic game state.

The most important thing to watch is which number the form returns. A 50% HP building reads as twice the base time, which matches the Omni Rust decay formula but not the in-game timer ticking down one layer at a time. Treat the result as a planning estimate and refill the Tool Cupboard before the in-game timer hits zero.

According to the Omni Rust Decay Calculator, the standard rust decay formula divides the material's base decay time by the current health percentage expressed as a decimal, which is the same shape this form uses for every material and HP input.

According to the official Facepunch Rust wiki entry on the Tool Cupboard, decay, and building privilege, the in-game decay timer reads Twig 1 hour, Wood 3 hours, Stone 5 hours, Metal 8 hours, and Armoured 12 hours once upkeep is gone, which is the current authoritative default the form's base-time table mirrors.

For a duration estimate where a base rate is divided by a remaining-fraction input, the Upload Time Calculator applies a similar divide-by-fraction pattern to estimate how long a partial file upload still has left at the current throughput.