Rust Furnace Calculator
How many furnaces you need, how long the smelt takes, and how much wood it burns. Or enter the furnaces you own, any mix, and see how long your ore takes.
What are you smelting?
Which furnace?
A large furnace smelts 5 times faster than a small one for the same wood.
How much sulfur ore?
Large Furnace ×2Smelt speeds
per ore · ore per minute| Ore |  Furnace | Large Furnace |  Electric Furnace | Cook time |
|---|---|---|---|---|
 Metal Ore | 3.3s · 18/min | 0.67s · 90/min | 2.0s · 30/min | 10s |
 Sulfur Ore | 1.7s · 36/min | 0.33s · 180/min | 1.0s · 60/min | 5s |
 High Quality Metal Ore | 6.7s · 9/min | 1.3s · 45/min | 4.0s · 15/min | 20s |
| Slots: wood · ore · output | 1 · 2 · 3 | 2 · 5 · 10 | 0 · 2 · 3 |
A furnace's speed is shared by every stack of ore in it, so splitting ore over more slots does not make it faster. Each cooking stack gets an equal share: one sulfur stack and one metal stack each get half, and two sulfur stacks with one metal stack give sulfur two thirds. A large furnace is 5× a Furnace; an electric furnace is 1.7× a Furnace. Wood is 30/min on both wood-fired sizes. Charcoal comes back from wood; these ovens will not burn charcoal as fuel.
Rust Furnace Ore Per Minute and Wood Burn
- Wood burn does not scale with smelt speed. A large furnace eats the same 30 wood a minute as a small one and puts out 5× the ore. Industrial ovens match their normal versions.
- Expect about 75 charcoal per 100 wood. Charcoal will not burn as fuel.
- Mixed ores share the cook slots. Sulfur plus metal on a small furnace was 18 sulfur and 9 metal a minute, not 36 + 18.
- Small oil refinery: 18 crude a minute → 54 low grade, 40 wood a minute.
Methodology
Tested in game on our own server: every oven, every ore, mixed loads and the refinery on crude. An electric furnace only cooks with power. Tested on the current version of Rust.