Calculating amount of firewood in a log?

[Poolco]

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

 

[mga]

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.

 

[acer saccharum]

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.

 

[Richard_]

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.

 

[Poolco]

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.

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!

 

[myzamboni]

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

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

 

[abohac]

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

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.

 

[turnkey4099]

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

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

 

[KsWoodsMan]

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.

 

[Husky137]

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.

 

[woodfarmer]

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.

 

[KsWoodsMan]

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.

 

[mga]

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.

 

[jrclen]

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)

 

[Husky137]

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.

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.

 

[Wood Doctor]

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.

 

[Husky137]

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.

 

[KsWoodsMan]

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 ?

 

[turnkey4099]

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 ?

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

 

[Wood Doctor]

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.