Furnace Guide: Smelting Rates and the Furnace Split Technique
Smelting one giant stack of ore at a time is slower than it needs to be. Splitting your furnace load fixes that.
The Furnace is one of the first real crafting stations you'll place, and understanding how it actually processes ore saves a surprising amount of farming time.
How the Furnace Works
Once crafted and placed, the Furnace can be operated by any nearby player and shows an empty grid. To use it, place wood in it and ignite it — it burns up to two wood at a time and produces the smelted version of whatever ore is loaded roughly every 30 seconds. You don't need to stay near it while it runs; it keeps smelting until it's turned off, runs out of fuel, or an output slot fills up with no room for the smelted material or resulting charcoal.
The Furnace Split Technique
New players often load one complete stack of a single ore type, which is actually slower than it needs to be. Instead, split your ore into three or four smaller stacks in the furnace — if you use four stacks, some other material may get pushed out of the furnace, but it won't disappear, just drop nearby. This "furnace split" trick meaningfully speeds up overall smelting compared to one giant stack.
Crafting Cost
The Furnace itself costs 50 low-grade fuel, 100 wood, and 200 stone. Each low-grade fuel craft produces 4 units and costs 3 animal fat plus 1 cloth, so 13 crafts (52 low-grade fuel) covers the requirement, at a total cost of roughly 39 animal fat and 13 cloth.
Repair Costs
With a Hammer: 27 low-grade fuel, 50 wood, 98 stone. With a Repair Bench: 25 low-grade fuel, 50 wood, 100 stone. Maximum condition loss is capped at 20%.
Smelting Rates
Conversion rates in Rust are usually 1:1. Wood itself burns at roughly 30 wood per minute (one wood every 2 seconds) as furnace fuel. Approximate smelting rates by ore type:
- Metal Ore → Metal Fragments — 5 wood fuel cost, ~6 metal fragments/minute yield, 1:1 ratio.
- Sulfur Ore → Sulfur — 2.5 wood fuel cost, ~12 sulfur/minute yield, 1:1 ratio.
- Wood → Charcoal — 1.33 wood fuel cost, ~22.5 charcoal/minute yield, 4:3 ratio.
- High-Quality Metal Ore → High-Quality Metal — 10 wood fuel cost, ~3 HQM/minute yield, 1:1 ratio.
These numbers can shift slightly with game updates, so treat them as a solid baseline rather than gospel — check in-game if something seems off.
Do I need to babysit the furnace while it's smelting?
No — once lit, it keeps working whether you're nearby or not, until it runs out of fuel, gets turned off, or an output slot has nowhere to put the result.
Why is splitting ore into multiple stacks faster than one big stack?
The furnace processes a limited amount per cycle regardless of stack size, so spreading ore across several smaller stacks lets more of it get processed per cycle rather than bottlenecking on one huge pile.
What's the fastest resource to smelt in bulk?
Sulfur ore has both a low fuel cost and a high yield per minute among the common ores, which is part of why dedicated sulfur smelting setups are popular for anyone planning to craft explosives.
Should I use a Large Furnace instead of a regular one?
For serious ore volume (especially sulfur for raiding), yes — a Large Furnace processes more at once and is generally worth the extra resource investment if you're smelting regularly rather than occasionally.