# Calculating amount of firewood in a log?



## Poolco (Oct 4, 2008)

I was thinking about how to calculate the amount of firewood (in cords) in a certain length log. Is the calculation simply;
1) Determine how many cubic feet there are in the log and then; 
2) Divide by 128(cubic feet in a cord).

Example: A log, 10 ft long, 2' average diameter
Calculation: 10' x 3.14 x 1 (Radius Squared) = 31.4 cubic feet in this log.
31.4/128 = .24 of a cord.

So if I use the above example and I fell 4 logs - 10 ft long log 2' average diameter, after bucking, splitting and stacking I should have about 1 full cord of wood stacked?

Is this the way it's suppose to work or am I missing something? I'm trying to figure out how many trees I need to fell this winter in order to supply my firewood for next year. I don't want to cut more than necessary.

Thanks


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## mga (Oct 4, 2008)

too many factors to consider to be accurate:

1. the size you split the wood. they always don't come out the same way.

2. the taper of the log in 10 foot lengths

3. the heating season. warm winter versus a cold winter

4. the efficiency of your wood burner

you would have to average the past couple of years to get a close proximity of how much wood you would need. trying to determine the exact amount is almost impossible.


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## acer saccharum (Oct 4, 2008)

You are on the right track, but you probably have a little over a cord of wood there. 

A cord of wood is a stack of wood measured 4x4x8 feet. No part of the definition sets the size of pieces. So take your 'average' logs that are 2 feet in diameter. If you cut them 8 feet long and then stack them 2 wide and 2 high you will have a stack of wood that -is- a cord.


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## Richard_ (Oct 4, 2008)

I copied this from http://salem.craigslist.org/grd/866648301.html
One cord of wood is 1,536 board feet. For instance an 18 inch diameter log, 20' long equates to 270 board feet . So you would need approximately 5 of those size logs.


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## Poolco (Oct 4, 2008)

mga said:


> too many factors to consider to be accurate:
> 
> 1. the size you split the wood. they always don't come out the same way.
> 
> ...



I know that I burn appx 3 cords of wood per season. What I'm trying to figure is how many cords are in a certain size log so I can get a close idea how many logs I need total that will eventually equal 3 cords total when split and stacked. 
The idea being that as I cut logs and stack them, I can measure the logs and simply calculate how many cubic feet of wood I have in the pile of un-bucked logs and then divide by 128 to determine how many cords are in the pile. Don't want to come up short!


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## myzamboni (Oct 5, 2008)

Poolco said:


> I was thinking about how to calculate the amount of firewood (in cords) in a certain length log. Is the calculation simply;
> 1) Determine how many cubic feet there are in the log and then;
> 2) Divide by 128(cubic feet in a cord).
> 
> ...



the piece you are missing is: A stacked cord of wood is ~25-30" airspace, so you are over a cord by your calculations.


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## abohac (Oct 5, 2008)

Poolco said:


> I was thinking about how to calculate the amount of firewood (in cords) in a certain length log. Is the calculation simply;
> 1) Determine how many cubic feet there are in the log and then;
> 2) Divide by 128(cubic feet in a cord).
> 
> ...


You are wasting too much time figuring and not enough time cutting. The fact of the matter is that you can not have too much wood for next year.


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## turnkey4099 (Oct 5, 2008)

Poolco said:


> I was thinking about how to calculate the amount of firewood (in cords) in a certain length log. Is the calculation simply;
> 1) Determine how many cubic feet there are in the log and then;
> 2) Divide by 128(cubic feet in a cord).
> 
> ...



I don't bother estimating number of trees. I know I need at least 6 cords so I keep cutting/splitting/stacking until I have 6 cords. Usually do several more to build up a reserve.

Now if you are ordering wood by the log, you are pretty well stuck with full loads anyhow.

Harry K


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## KsWoodsMan (Oct 5, 2008)

A stacked cord of firewood measures 128 cubic feet. In that cord there is wood, bark *and* airspace. It is accepted that a cord of firewood is only 80-85 cubic feet of solid wood. I have yet to see a stack of wood that didnt have any airspace. I see some decent stacks but none that good.

If the logs you described were each approx 32 cubic feet of solid wood then just 3 of them would equal more than a cord of wood after being cut to length, split to size and stacked tightly in rows. About an 1/8th of a cord more. YMMV

I have seen an estimator of DBH versus number of _trees_ needed to make a cord of firewood. I've been looking but don't seem to come up with a link. The accuracy of it depends on how much or little waste you practice when harvesting firewood. If you are only going to harvest the trunkbelow the first fork it takes more trees. If you cut limbs down to 2 - 2 1/2 inches it will take fewer trees.

If you know the cubic feet of each log figure on 80 cubic feet of solid wood in a cord of firewood. Once it is cut and split it will come out to a full cord. I will throw on a few extra pieces just to be sure in case I do sell a stack.


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## Husky137 (Oct 5, 2008)

Richard_ said:


> I copied this from http://salem.craigslist.org/grd/866648301.html
> One cord of wood is 1,536 board feet. For instance an 18 inch diameter log, 20' long equates to 270 board feet . So you would need approximately 5 of those size logs.



That Craigslist info is wrong. Generally accepted rule of thumb here in the northeast is roughly 500 BF (international 1/4 inch scale) equals 1 cord (128 cubic feet) of cut, split and stacked firewood. I have used this measuring method hundreds of times and it is very accurate.


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## woodfarmer (Oct 5, 2008)

that is a good question, i was trying to figure out which way to go..sell my logs for $50 cord at landing, or cut split and sell for $300 cord. if it takes one good tree to make a cord and almost an hour to fell, limb, skid and stack, i shouldn't quit my day job.


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## KsWoodsMan (Oct 5, 2008)

Husky137 said:


> That Craigslist info is wrong. Generally accepted rule of thumb here in the northeast is roughly 500 BF (international 1/4 inch scale) equals 1 cord (128 cubic feet) of cut, split and stacked firewood. I have used this measuring method hundreds of times and it is very accurate.



I dont know about the conversion from Board feet to cords.

But I know they are a long way from being right about needing 5 of those 18" logs 20 feet long to make a cord of firewood. If the average Dia. is 18" , it only takes 3. Sounds like they are giving away some wood. 

I wonder if I drove up there and set them straight would they load my truck for free since I was saving them money ? 


Nah, they know what they are doing and I have enough wood for now.


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## mga (Oct 5, 2008)

Poolco said:


> I know that *I burn appx 3 cords *of wood per season. What I'm trying to figure is how many cords are in a certain size log so I can get a close idea how many logs I need total that will eventually equal 3 cords total when split and stacked.
> The idea being that as I cut logs and stack them, I can measure the logs and simply calculate how many cubic feet of wood I have in the pile of un-bucked logs and then divide by 128 to determine how many cords are in the pile. Don't want to come up short!




so....ummm....if you cut and split 3.5 cords or even 4 cords of wood.....what happens then?


most of the people here are working on their 09-10 stock piles already.


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## jrclen (Oct 5, 2008)

I don't know if this helps you at all but I was bored this year, retired and all, so I kept track of what I was doing with the wood this summer.

I cut out back in our oak woods and haul the blocks to the shed where the splitter is set up. I haul with a International Harvester Farmall B that is just a little older than I am, and a trailer made from a 1950's chevy truck box. That box heaping full is a load in my chart. The trees are dead oaks. My wood shed holds a bit over 10 cord. I burn about 7 or 8 per year.

FIRE WOOD 2008

6-1	2 loads left from 2007
6-2	3 loads from west corner 2 small trees and 1 medium tree
6-14	3 loads from west corner 1 small tree and 1 medium tree
6-20	4 loads from west corner 1 large tree
6-25	1 load from west corner limbs already on the ground
7-10	1 load from out back 2 small trees
7-15	3 loads from east 1 med tree 1 small tree
MAIN SHED FULL (7.3 CORDS)
7-17	1 load from east 1 small tree
7-28	2 loads from out back west 1 large tree
8-5	0 loads from dead tree near propane tank

18 TRAILER LOADS TO FILL MAIN SHED FOR THE YEAR
8 TRAILER LOADS TO FILL RESERVE SHED
128 CU FT PER CORD .4 CORD PER TRAILER LOAD
480 CU FT SECTION 1 NORTH (3.8 CORDS)
448 CU FT SECTION 2 MIDDLE (3.5 CORDS)
416 CU FT SECTION 3 SOUTH (3.3 CORDS)


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## Husky137 (Oct 5, 2008)

KsWoodsMan said:


> I dont know about the conversion from Board feet to cords.
> 
> But I know they are a long way from being right about needing 5 of those 18" logs 20 feet long to make a cord of firewood. If the average Dia. is 18" , it only takes 3. Sounds like they are giving away some wood.
> 
> ...



Definitley sounds like they are giving wood away. If the tip diameter was 18 inches they could still get away with 2 of those logs, probably even slightly less.295 BF intl or 270 scribner.


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## Wood Doctor (Oct 5, 2008)

Husky137 said:


> That Craigslist info is wrong. Generally accepted rule of thumb here in the northeast is roughly 500 BF (international 1/4 inch scale) equals 1 cord (128 cubic feet) of cut, split and stacked firewood. I have used this measuring method hundreds of times and it is very accurate.


500 bd ft = one solid mass of 72,000 cubic inches or 41.67 cubic feet.

One cord of wood is 128 cubic feet of logs stacked, or about *115 cubic feet of solid mass* after knocking out 10% air in the stack.

That means you need at least (115/41.67) x 500 = 1,380 bd feet of lumber to equal a cord of stacked logs. Sounds like you are talking about a face cord, and I fear that confusion has plagued us all for at least a millenium.


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## Husky137 (Oct 5, 2008)

No, I am not talking about a face cord. Never seen a face cord,never sold a face cord.


I am talking about BF in a log measured with a log rule (international 1/4 inch scale), which isn't about exact volume, but projected yield, based on slab waste,taper and saw kerf.

Firewood does not get sold by anything but a true 128 cubic foot cord here in Massachusetts.


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## KsWoodsMan (Oct 5, 2008)

Wood Doctor said:


> One cord of wood is 128 cubic feet of logs stacked, or about *115 cubic feet of solid mass* after knocking out 10% air in the stack.



Maybe you can let the rest of us in on how you came up with this ?

Every time I run it with equally sized round pieces I come up with 100.48 cubic feet of wood in the stack. 1 4ft log 8 feet long = 100.48 cubic feet, 4 2 foot dia logs 8 feet long = 100.48 cubic feet 576 2" pieces 8 feet long = (you guessed it) 100.48 cubic feet. Wood comes in irregular shapes, especially if split. This will give us more airspace. Then there is the bark from the tree. This bark is included in the legal description of a cord as is the airspace.

In a perfect world, I can see this working out to 115 cubic feet *IF* you had perfectly round cylidrical pieces all the same diameter. Each one stacked perfectly to exacly a perfect 4 feet tall , 4 feet wide and 8 feet long. Then in the gaps between those pieces you were to stack in pieces that were all exacly 41.4213562373095048801688724209698 % the diameter of the first set in the stack. So that one layer of the larger pieces were laid down in the stack then a layer of the smaller set, then a larger set then a smaller set, ad nausium. Till the last layer of larger pieces was put in to finish out to the cord.

This isnt a perfect world. All the pieces aren't uniform. With firewood or logs you arent going to get 115 cubic feet of wood in a stack. If you are, I cant imagine it being productive or profitable. Maybe you are spending too much time stacking, when you could be more productive elsewhere. I wouldnt question 85 or even 90 cubic feet of wood in a stack but...... 115 ? *115 ?*


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## turnkey4099 (Oct 6, 2008)

KsWoodsMan said:


> Maybe you can let the rest of us in on how you came up with this ?
> 
> Every time I run it with equally sized round pieces I come up with 100.48 cubic feet of wood in the stack. 1 4ft log 8 feet long = 100.48 cubic feet, 4 2 foot dia logs 8 feet long = 100.48 cubic feet 576 2" pieces 8 feet long = (you guessed it) 100.48 cubic feet. Wood comes in irregular shapes, especially if split. This will give us more airspace. Then there is the bark from the tree. This bark is included in the legal description of a cord as is the airspace.
> 
> ...



I don't have any figures to back it up but I agree. 10 per cent air in a stack is way underestimated.

Harry K


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## Wood Doctor (Oct 6, 2008)

turnkey4099 said:


> I don't have any figures to back it up but I agree. 10 per cent air in a stack is way underestimated.
> 
> Harry K


Well, KSW and Harry, I finally got your attention. So, let's revise my figures, and I'll *double* the waste for air, leaves, twigs, etc. in the stack:

500 bd ft = one solid mass of 72,000 cubic inches or 41.67 cubic feet.

One cord of wood is 128 cubic feet of logs stacked, or about *102 cubic feet of solid mass *after knocking out 20% air and waste in the stack. (You guys must pack pretty loosely and have lots of knotty wood, twigs, and bark in your stacks with voids everywhere or just do a random pile.)

That means you need at least (102/41.67) x 500 = 1,228 bd feet of lumber to equal a cord of stacked logs. That is still a far cry from only 500 bd ft in a cord of wood. Bottom line, in order to shrink a cord of wood down to 500 bd ft, I have to waste away two-thirds of the volume in the stack? Give me a break.


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## Husky137 (Oct 6, 2008)

You stick to your theoretical calculations based on your hypotheses (most of which involve incorrect assumptions) and I'll stick to real world experience. Yours is obviously limited enough that you can't wrap your head around the conversion that I have tried to politely explain. Just because you can't make it work in a nice little formula on the internet, doesn't mean it doesn't work in a real world application. My conversion stacks up every time.

FWIW, another accepted concept in the firewood industry states that 128 cubic feet of cut split and stacked firewood, only contains aproximately 80 cubic feet of solid wood.

Now you can give me a break doc.


I'd love to chat some more, but I have to go cut some real wood.


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## Wood Doctor (Oct 6, 2008)

Husky137 said:


> FWIW, another accepted concept in the firewood industry states that 128 cubic feet of cut split and stacked firewood, only contains aproximately 80 cubic feet of solid wood.
> 
> Now you can give me a break doc. I'd love to chat some more, but I have to go cut some real wood.


OK I'll go all the way down to 80 cubic feet of solid wood that's 37.5% waste in air, bark leaves, knots, and whatever other useless trash is in the pile (skunks, mice, rats, snakes, bugs etc). I can hardly believe that, but if you say so, I will try my best.

80 cubic feet of solid wood is *960 bd ft*--not 500 bd ft because there are 12 bd ft in a cubic foot. My case rests.


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## KsWoodsMan (Oct 6, 2008)

Wood Doctor said:


> Well, KSW and Harry, I finally got your attention. .



Ed, you dont need my attention. 

I'm not wasting my time educating someone that thinks they are smarter than me.

Stop following me around looking for a "debate". I'm happy for you that you can run a spreadsheet that says you can get this much wood in your piles. In real practice it isn't going to happen. If you have all the time in the world maybe. Maybe if you skin off all the bark and waste the knots and ends then split only into quarters so they all lay perfectly with no gaps. It could happen. Do as you like , say what you please about my posts. I have lost interest in this conversation or any other from you in the future. I will politely smile as I continue to ignore you. 

Good day.


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## Wood Doctor (Oct 6, 2008)

KsWoodsMan said:


> Ed, you dont need my attention.
> 
> I'm not wasting my time educating someone that thinks they are smarter than me.
> 
> ...


Are you kiding me? What on earth gave you the idea that I thought I was smarter than you? I never said that, but if I implied it, then please forgive me. I use spreadsheets only because I spent several years teaching myself how to work with them and eventually wrote three books on Excel spreadsheet applications.

C'mon, Alfred E. Newman, bury the hatchet. We are all woodcutting buddies in this forum, and discussions are needed by all. Please stop taking things personally.


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## cityevader (Oct 6, 2008)

I'll jump in with something. A few years ago I got nearly two full pickup loads of end cut lumber, everything from 2x4 to 6x12, from the local lumber yard. 
They were thrown into the truck, then neatly and tightly stacked, like a giant game of Tetris, into my wooden shed. It seemed amazingly small compared to when it was thrown into truck. It stacked, vaguely remembering, something like 3 foot square and maybe 6 feet tall......zero, i mean zero air gaps.
That winter,the corner pier underneath the stack sunk nearly 2inches, it was that heavy.

What does this have to do with board feet vs cords? No idea...
I like stories.


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## Backwood (Oct 6, 2008)

reading this got me to wondering too. If I took wood that came off the bandsaw , sawed to 1 inch thick and 8' long and stacked it without stickers 4' wide 8' long and 4' tall that would be ( 4 x 8 x 48 ) that would give me a stack of lumber containing 1536 board feet with no airspace. subtract what ever you think the voids would add to, 20% - 30% ??????? if you figured 20% voids it should be close to 1228' 30% voids should be 1075'
I guess it would make a big difference in how tight you stacked it, I worked for a guy 20 years ago that wanted to throw it in the truck just as crossed up as possible to use less pieces of firewood per truckload, he might have been able to stack it with 60% voids


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## turnkey4099 (Oct 7, 2008)

KsWoodsMan said:


> Ed, you dont need my attention.
> 
> I'm not wasting my time educating someone that thinks they are smarter than me.
> 
> ...



What he said. 

Harry K


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## The Lorax (Oct 7, 2008)

So this would be a 1/2 cord roughly? 
4x4x4 stacked with almost no air gaps.


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## jrclen (Oct 7, 2008)

The air that is included in my wood pile contains the oxygen needed for my fire to burn. So it is part of my fuel equation. I leave the twigs and leaves in the woods, they are to hard to pick up. opcorn:


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## KsWoodsMan (Oct 7, 2008)

The Lorax said:


> So this would be a 1/2 cord roughly?
> 4x4x4 stacked with almost no air gaps.




ROFLMAO - Yeeip ! It is exactly no less than 1/2 cord. But it is too pretty to burn.


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## cityevader (Oct 7, 2008)

What if i traded my "half cord" of end cut lumber for a "half cord" of as-tightly-packed-as-i-can-get oak branch cuttings (say...2" diameter or less)? Nary a straight one in the bunch, but still "tightly packed". I guarantee it'll weigh at a bare minimum 30% less!!

Can we kill this thread with an MTV Deathmatch? Have some claymation characters duke it out, woodpile to woodpile?


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## KsWoodsMan (Oct 8, 2008)

Duke it out over what ? how much wood in a log ? 
nah ! we are ALL right ? We all just do things differently.


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## Husky137 (Oct 8, 2008)

Wood Doctor said:


> 80 cubic feet of solid wood is *960 bd ft*--not 500 bd ft because there are 12 bd ft in a cubic foot. My case rests.



It is a good thing that you rested your case because you assumptions are wrong. You don't understand how a LOG RULE works. When BF is calculated to project yield in a log they use a LOG RULE, International,Scribner,Doyle, whatever. They don't get their slide rule out and figure the volume of the cylinder.(which would be pointless since no log is a perfect cylinder. You've made the same mistake as the Craigslist guy.

There are not 12 BF in a cubic foot unless it is a solid chunk. If it is sawn, you lose yield to saw kerf and edge trimming.

So to try and explain again.

If I take enough logs that measure out with an international log rule to yield 500BF of sawn 4/4 lumber and cut,split and stack them for firewood instead, I will have roughly 128 cubic feet of stacked firewood.


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## Wood Doctor (Oct 8, 2008)

Husky137 said, "If I take enough logs that measure out with an international log rule to yield 500BF of sawn 4/4 lumber and cut, split, and stack them for firewood instead, I will have roughly 128 cubic feet of stacked firewood."
------------------
:agree2: I agree with this statement 100%. By the time you slab off all the unusable wood that is perfectly good firewood but not usable for 4/4 lumber, that is exactly what you likely will have left--about 500 BF.

The amount of biomass wasted to make 4/4, 5/4, 6/4, etc. lumber is huge. If it's rough sawn, you are still not even through because that's usually planed further.


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