Factorio furnaces per belt: smelting ratios
A full yellow belt of ore feeds 48 stone furnaces or 24 steel or electric furnaces. Double that for a red belt, triple it for a blue belt and quadruple it for a turbo belt.
The numbers behind it
Iron and copper plates take 3.2 seconds to smelt. A stone furnace has crafting speed 1, so it makes 1 รท 3.2 = 0.3125 plates per second. Steel and electric furnaces have crafting speed 2 and make 0.625 plates per second. Each plate uses one ore, so a furnace eats ore at the same rate.
| Belt | Items per second | Stone furnaces | Steel or electric furnaces |
|---|---|---|---|
| Yellow (transport belt) | 15 | 48 | 24 |
| Red (fast transport belt) | 30 | 96 | 48 |
| Blue (express transport belt) | 45 | 144 | 72 |
| Green (turbo transport belt, Space Age) | 60 | 192 | 96 |
Most layouts put half the furnaces on each side of the input belt, so a yellow-belt column of 24 steel furnaces has 12 on each side.
Steel plate
Steel takes 16 seconds and 5 iron plates. A steel or electric furnace therefore makes 0.125 steel per second and uses 0.625 iron plates per second, the same rate an iron furnace produces. That gives a simple rule: one steel furnace for every iron furnace feeding it. A yellow belt of iron ore needs 24 furnaces for iron and 24 more for steel, and gives 3 steel per second.
Modules and beacons
Speed modules raise crafting speed, so fewer furnaces fill the same belt. Two speed module 3 in an electric furnace add 100% speed, which halves the furnace count: 36 instead of 72 for a blue belt.
Blueprints that use these ratios: smelting blueprints.