Smelting Calculator
Calculate exact smelting times, wood fuel needed, and charcoal output. Compare small furnace, large furnace, and electric furnace.
Small Furnace
6 total slots (3 ore), uses wood
Large Furnace
18 total slots (6 ore), uses wood, 2x speed
Electric Furnace
3 input slots, no wood, 5 rW power
Optimal Furnace Ratios (Large Furnace)
Metal Ore
Optimal split: 6 ore + 1 wood slots.
1 wood per 2.5 ore smelted. Remaining slots for output (metal frags + charcoal).
Sulfur Ore
Same as metal: 6 ore + 1 wood slots.
Tip: smelt sulfur + metal together for efficiency.
HQM Ore
Needs more fuel: 6 ore + 2 wood slots.
HQM takes 2x longer to smelt, burns 2 wood per ore.
Optimal Slot Layout (Large Furnace - 18 Slots)
In Rust, furnace slots are shared between ore, wood, and output. Here is the recommended layout for maximizing throughput:
Metal / Sulfur (Standard)
Burns 1 wood every 2.5s, smelts 1 ore every 2.5s per slot. Ratio: 1 wood per 2.5 ore.
Metal / Sulfur (Max Ore)
Requires babysitting -- move output frequently. 2x ore throughput but needs monitoring.
HQM
HQM takes 5s per ore in large furnace. Burns 2 wood per ore smelted.
Electric Furnace
No wood, no charcoal. Output goes to separate slots. Fastest per-item but limited input.
Rust Smelting Guide
Smelting is the process of converting raw ores into usable materials using furnaces. Rust has three furnace types: the Small Furnace (craftable at workbench level 1), the Large Furnace (found at monuments), and the Electric Furnace (requires electricity but no wood fuel).
Furnace Comparison
The Large Furnace smelts at 2x the speed of a Small Furnace and has 18 slots vs 6. It's the most efficient option for bulk smelting. The Electric Furnace requires no wood and smelts fastest per-item, but only has 3 input slots and needs a constant power supply of 5 rW. For most players, a combination of Large Furnaces for bulk and Electric Furnaces for convenience is optimal.
Charcoal as a Byproduct
Wood-burning furnaces produce charcoal as a byproduct. Charcoal is essential for crafting gunpowder (30 charcoal + 20 sulfur = 10 gunpowder). A single large furnace run often produces enough charcoal for your gunpowder needs, making it important to plan your smelting to maximize charcoal output alongside your ore processing.