Calculate the Cost of Wood and Bark in Stack of Firewood
Did you get what you paid for? How much did you end up paying for the air that is included in your cord of firewood?
There is no real-life use for this unless you are trying to calculate the amount of Btu's your cord of firewood potentially could produce or to see if you actually came close to the number of cords you purchased.
You buy an "x" of cords of firewood at a certain price and you come home and stack it up neatly and measure the woodpile and calculate what you have. Based on that one cord = 128 cubic feet, how many cords did you end up with? What was the price you paid for wood and bark and how much did you pay for the air in your stack of firewood?
A cord of firewood has a gross volume of 128 cubic feet. An area of 8' long 4' high and a depth of 4' adds up to 128 cubic feet as of course, many other measurements will too. Obviously, there will be a certain percentage of air in that area occupied by your stacked firewood. The packing factor will determine how much air there is in your pile of wood. 25% as a packing factor is not uncommon and at that rate, a cord of firewood with a gross volume of 128 cubic feet would have a net volume of 96 cubic feet of wood plus bark meaning that 32 cubic feet of that space would be occupied by air.
In addition to the packing ratio, if you bought your cord of firewood in the green state, there will be a certain amount of shrinkage to your pile. As the wood is drying from a high moisture content (MC) to a desirable MC of 20% or less, it reaches the Fibre Saturation Point (FSP), the point at which all of the free water is removed from the wood and the wood will start to shrink. FSP for most species is reached when the wood dries to a 28 / 30% MC.
Volume metric shrinkage of wood varies by species and to keep it simple this calculator uses a preset value of 3% as the factor for shrinkage from FSP to 20% MC