Whether you’re building your first factory or an advanced megabase, smelting ratios determine how many furnaces you need per belt. Here’s the math.
The Core Concept
A transport belt carries 7.5 items/second (15 items/second for fast belt, 22.5 for express belt).
A stone furnace smelts 1 plate per 3.2 seconds = 0.3125 plates/second. An electric furnace smelts 1 plate per 1.6 seconds = 0.625 plates/second.
Iron and Copper Smelting
| Belt Type | Plates/sec | Stone Furnaces | Electric Furnaces |
|---|---|---|---|
| Basic belt (half) | 3.75 | 12 | 6 |
| Basic belt (full) | 7.5 | 24 | 12 |
| Fast belt | 15 | 48 | 24 |
| Express belt | 22.5 | 72 | 36 |
Steel Smelting
Steel needs 5 iron plates and takes 17.5 seconds in a stone furnace.
| Setup | Steel plates/sec | Furnaces needed |
|---|---|---|
| Basic | 0.28 | 1 furnace = 1 steel at a time |
| Optimized | 1.0 | 6 electric furnaces + beacon setup |
Pro tip: Steel is slow. Don't try to make large amounts of steel with stone furnaces. Electric furnaces or steel furnaces are highly recommended.
Visual Layout
A proper smelting column (simplified description):
Iron ore belt arrow Furnace Furnace Furnace... arrow Plate output belt arrow Chest or next assembler
Design principle: Always leave space to upgrade from stone to steel to electric furnaces without rebuilding the entire column. Your smelting output feeds directly into the main bus, so plan your bus width to match your furnace capacity.
Beaconed Smelting (Megabase)
With speed module 3 in furnaces plus speed beacons:
| Setup | Plates/sec per furnace | Furnaces for 1 belt |
|---|---|---|
| Beaconed electric | ~2.5 | 3 furnaces per half-belt |
Next: Production Ratio Reference — all ratios in one table.