Is there any concensus on what the most efficient size of charcoal pit is?

[Broccoli Clock]

I've seen all sorts of sizes (..madam!) from the classic 2x2 up to almost warehouse sized, yet I've noticed that the larger I build my charcoal pit, the less efficient it becomes. By efficiency I'm not meaning speed of burn but in the return of charcoal. I've done a little testing, nothing extensive, yet it seems I lose less of a % by doing multiple 2x2 pits rather than one large one.

I've read through the wiki and watched other streamers, and it seems like there is no hard or fast way to guarantee the best results. It's not a big deal, and I am not necessarily looking to min/max the situation, just wondering if there has been someone who has tested this.

 

 

 

[Pascaloubicou]

Look like when you are doing the biggest size possible you loose a lot but it's just an illusion no ?  For me i guess it's a matter of time you want to spend filling the pit and maybe accident are way more manageable with a smaller pit.

[Broccoli Clock]

11 minutes ago, Pascaloubicou said:

.. but it's just an illusion no ? 

That's the thing, is it?

I initially thought the same, yet when comparing in my (limited) testing it seems the 2x2 is the more efficient in terms of returning charcoal.

Is multiple pits more of an effort than larger ones? I suppose that all depends on whether you have the wood as, as big or small your as charcoal pit is, it's chopping the wood that is the real time sink.

[Pascaloubicou]

25 minutes ago, Broccoli Clock said:

That's the thing, is it?

Hopefully.  And the wiki say that :

• The yield for each stack of 32 firewood is between 4 and 7 charcoal, the average yield of each stack is 5.5 charcoal.

[Michael Gates]

I've never seen anyone check the numbers, which would require burning.. I dunno, probably a couple dozen pits at each of at least three sizes. Personally I'm going to stay with the 2x2x2 pits with a tab, because that's an amount of wood you can cut in a few game hours with an iron axe. Go out for an afternoon, whack some trees, dump 'em in the hole, light 'em, back for supper.

[TheMadGod]

I usually make charcoal three times a year. Got a huge charcoal kiln just outside the house, takes ages to fill but once filled, you got coal coming out of your ears. It takes hours and 10 flint shovels to dig it all up. Maybe, I am making it too big, but usually, i dedicate that time, then i can create tons of stuff before having to worry. I'd say, smaller is more efficient since  you can basically fill that up in a few RL minutes and then burn it...but I like it impressive.

[Thorfinn]

I've switched to mostly 1-deep by whatever I need to use up all the wood. Might end up switching back, don't know/ The reason I switched was one of the recent releases where the sliding charcoal would just disappear, rather than piling up on a lower level.

I know it's supposed to just put all the loss into the top block, but it sure feels like I'm losing less when there's not a charcoal block below.

Besides, it was a pain because as I'd excvate the pit, I would have to keep converting the soil to packed soil, then using that to keep the walls from falling on me. One deep, all that hassle goes away.

[TheMadGod]

I put down a chest with packed dirt sufficient to cover the whole kiln just near it. So i never have to bother making it anew. I never make coal before I find a permanent spot to settle, tbh, so I never bother making small kilns. Wood is usually aplenty and most of the time goes into creating flint axes.

[LadyWYT]

The general loss ratio seems to be fairly consistent, regardless of pit size. I say that just from making a rough guess based on what I've dug out of my charcoal pits, not because I've sat down and crunched every number.

That being said, I'd wager the "most efficient" depends heavily on the context of how much you need versus how much effort you want to put into it. A giant pit will net you a LOT of charcoal(like, I think I built a 7x7x7, which isn't max size, and got almost two full crates of charcoal), but will also take a significant effort to fill. A small pit is easily filled, but isn't very useful if you need a lot of charcoal.

I would say small pits are the most efficient in the early game, with moderate-size pits probably being the most efficient overall. They aren't as much hassle to fill as the huge pits, and provide decent amounts of charcoal per firing, meaning that it's easy enough to fire the pit 2-3 a week at most. Of course, if you'd rather just have a couple crates of charcoal after one firing, and not need to bother with it for a long time, then making a huge pit will probably be a more efficient use of your time.

[Lanceleoghauni]

my 5x5x3 takes forever to load and unload (much less now that I have iron tools, I suspect.) But given that I'm up to working iron now, between blooming, working those blooms, and shaping it really is proving to be necessary if I don't want to be wasting all my time firing small batches of charcoal

[Dark Thoughts]

Pretty sure it's just a percentage range, so larger piles may look worse at the end but efficiency wise there's no real difference. I guess you do save a bit of firewood on the firepits though. But if you really want to know, you can check the code.

[Maelstrom]

Why bother with dirt topping?  Fire up some glass to top the pit with.  It's the easiest way to make sure each stack is maximized to prevent fire and an easy indicator when the charcoal is ready to be gathered.  Given the high cost of firing steel, I've found a single firing of a 6x6x4 pit provides about the right amount of charcoal to run two cementation furnaces simultaneously.  

If you build a charcoal pit above ground, making the faces of glass would be recommended, but it's a bit more impractical to check the top for any incomplete firewood stacks.

I've found the quickest way to load a charcoal pit is to have a stack of items like sticks and fill my inventory with logs.  Leave one space in the hotbar open for filling with firewood but replace a stack of logs with a stick to prevent that inventory slot from filling with firewood.  The chopped firewood will automatically fall to the ground.  Stand near said pile of firewood entities and begin placing firewood from the single hotbar slot.  It will auto-refill with more firewood.  My 6x6x4 pit requires exactly 2 trunks of logs to fill which makes 144 stacks of firewood and takes forever filling it without this handy auto-refill technique.

[Dark Thoughts]

9 hours ago, Maelstrom said:

Fire up some glass to top the pit with.  It's the easiest way to make sure each stack is maximized to prevent fire and an easy indicator when the charcoal is ready to be gathered.

What for? The pit stops smoking when it is done. There's absolutely no need to waste glass on this, since the pit does not function like a real life charcoal pit.

[Never Jhonsen]

13 hours ago, Maelstrom said:

Fire up some glass to top the pit with.

4 1/2 years of playing this game and not once did I think of doing that Usually I make a 5x5 that’s 7 deep, and with my current home being under the surface of a forest, making a wall of glass shared with my charcoal pit would make for a great aesthetic

[Ceepert]

I would assume it just looks like you are missing more. Lets say you loose 10% volume. With a 2x2x2 thats not even a full block, while with a 3x3x3 you are already loosing almost 3 blocks. So the amount of missing blocks would increase by ~3x but the area in which the block are removed goes only from a 2x2 to a 3x3 so from 4 to 9 so ~2x (because the block are obviously only being removed from the top (you know, gravity)

So it looks like the 3x3x3 looses more, but yes thats just an illusion.
An extreme test case would be making something like a 2x2x8, so a tall tower of firewood into the ground.

[Thorfinn]

Fair, @Ceepert

I agree it may well be just that it seems to be that way. What I'm saying is that I rarely see a 1x1 reduced to a 4-high stack. That should happen a full 25% of the time. Why doesn't it? Why is it instead skewed to 6 or 7 layers? I can't answer that, but it strains credulity that I am consistently just that lucky.

[Maelstrom]

I wonder if the game is coded to convert 100% of the firewood to charcoal under the top layer of firewood.  That top layer gets <100% conversion to charcoal.

[Maelstrom]

14 hours ago, Dark Thoughts said:

What for? The pit stops smoking when it is done. There's absolutely no need to waste glass on this, since the pit does not function like a real life charcoal pit.

You seem to have totally missed the primary reason for glass - checking for gaps in the stack of firewood.

[Broccoli Clock]

5 hours ago, Maelstrom said:

I wonder if the game is coded to convert 100% of the firewood to charcoal under the top layer of firewood.  That top layer gets <100% conversion to charcoal.

I had a 3(w)x3(l)x4(h) pit and the top two layers of one corner were gone, as well as a decent chunk of most of the top layers. Was it within the expected ratio? No idea, didn't count, but it certainly seems like it's possible to "lose" more than the top layer.

In fact, it was that which prompted me to ask this (I should have started it in the questions subform, though).

 

[Maelstrom]

I run a 6x6x4 and seem to have three full stacks of charcoal with a partial stack on top.  Sometimes that partial stack has no layers, though.

[CastIronFabric]

Well if you factor in Opportunity Cost it become a complicated formula.

So while spending days getting it set up you could be doing something else and ends up finding you Black Coal in the process.

 

[Maelstrom]

Days?  Not even close.  It takes less than one in game day to set up a moderate charcoal pit (7x7x6 or less) including digging and replacing the sides of the pit if soil instability is active.  Not much opportunity lost. 

[Dark Thoughts]

On 3/26/2025 at 4:19 AM, Maelstrom said:

You seem to have totally missed the primary reason for glass - checking for gaps in the stack of firewood.

I just don't see how you get gaps in the first place.

[Maelstrom]

Gap meaning an incomplete stack of firewood. One misclick that puts 2 logs back in an inventory will turn a charcoal pit into a bonfire.  This is what I am talking about for the glass ceiling.

[Dark Thoughts]

15 hours ago, Maelstrom said:

One misclick that puts 2 logs back in an inventory will turn a charcoal pit into a bonfire.

Well, okay. But that's a "you" problem. The amount of times I've done that is literally zero.