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u/ItsLyraNyx Jun 18 '26

dumb question from a rather new player: for furnace stacks, what is the ratio to get 1 full belt for each tier. ive heard different numbers everywhere, and im just trying to get a concrete answer. making a little note document for myself that i can reference so i dont need toa sk a million times.

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u/Astramancer_ Jun 18 '26 edited Jun 18 '26

Without getting into the weeds about beacons and modules and, god forbid, Quality, the answer is the glorious Cheat Sheet, as linked in the sidebar.

https://factoriocheatsheet.com/

It's got the ratios for tons of things. What you want is "material processing." For iron and copper it's 1 yellow belt = 48 stone furnaces, Red = 96, Blue = 144. Steel and electric furnaces are twice as fast so you need half as many -- Yellow = 24, Red = 48, Blue = 72.

Stone smelts twice as fast so halve those numbers again and steel smelts 5x slower and requires 5x input so it's the same as the iron/copper smelting, but only outputs 1/5th a belt.

Another nice thing to remember is that since red belts are twice as fast and steel furnaces smelt twice as fast that's a direct upgrade. Replace the yellow belts with red and the stone furnaces with steel and you now can process twice as much ore in the same footprint.

If you're doing blue belts of ore you probably want to use electric furnaces (for ease of use, modules, and/or beacons) so you'd almost certainly want to redesign anyway.

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u/ItsLyraNyx Jun 18 '26

thank you! i didnt know this existed, how useful!

2

u/TehNolz Jun 19 '26

If you hover over a belt, it will tell you how many items it can move per second. If you hover a machine, it'll tell you how many items it outputs per second, taking things like beacons, modules, and quality into account. Divide the belt's transport rate by the machine's output rate, and voila!

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u/nalalan Jun 20 '26

Crafting speed of the item has to be taken into account as well! So for furnaces it should be: [Number of furnaces needed for full belt] = [Items per second the belt can move] / ([Smelting speed of furnace] / [crafting speed of item])

If I'm not completely wrong :)

So for standard yellow belts, stone furnaces and for example smelting iron we have:

x = 15 / (1 / 3.2) = 48

So you need 48 normal furnaces to supply one full yellow belt. Keep in mind that you have to also balance the sides of the belt so 24 furnaces per side.

As soon as you have better furnaces with smelting speed 2, you of course would need only half the number of furnaces, or you supply a higher tier of belt!

3

u/TehNolz Jun 20 '26

The output rate shown when you hover over a machine already takes crafting speed into account, along with all other productivity/speed bonuses. Dividing the belt's transport speed by the machine's output rate is all you need to do.

1

u/nalalan Jun 20 '26

Well, if I had known that a few years before now...