Spike's Calculators

# Cost of Wood and Air in your Stack of Firewood

Did you get what you paid for? How much did you pay for the air and bark in your stacked cord of firewood? It is expected when you buy a cord of firewood to pay for a stacked cord. In addition to wood and bark, this cord of firewood will include a certain amount of air.

There is only real-life use for this if you are trying to calculate the amount of Btu's your cord of firewood potentially could produce or to see if you came close to the number of cords you purchased.

You buy an "x" number of cords at a specific price, and you come home, stack it up neatly, measure the woodpile, and calculate what you have. Based on that one stacked cord = 128 cubic feet, how many cords do you have? If they charged you two dollars per stacked cubic foot of wood, how much did you pay for the air in your stack of firewood?

### Packing ratio

A cord of firewood has a gross volume of 128 cubic feet. A stack eight feet long, four feet high, and a depth of four feet adds up to 128 cubic feet. And, of course, many other combinations of measurements will too. There is always a certain percentage of air and bark in the area occupied by your stacked firewood. How it is stacked and how tight the firewood fits together will determine how much actual wood there is in your stack (packing factor). This packing factor will determine the air in your wood pile. 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, meaning that 32 cubic feet of the stack's space is air and bark.

### Shrinkage

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 high moisture content to the desired moisture content of 20% or less, it reaches the wood's fibre saturation point (FSP). When the wood reaches FSP, its volume starts to shrink. FSP for most species occurs when the wood dries from a 28 to 30% moisture content.

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% moisture content.

### Firewood Cost Calculator

Green or Seasoned Wood Green Seasoned
Cost per Cord \$
Length of Woodpile ft inch
Height of Woodpile ft inch
Depth of Woodpile inch
Packing Ratio %

#### Results:

 # of Cords in Pile cords Cubic Feet of Wood and Bark in Pile ft³ Cost for Wood and Bark \$ You Paid \$ for Air

#### Calculator

1. select if the firewood was green or seasoned at the time of purchase
2. the "per cord price" you paid
3. the length measurement of your stack of firewood in feet and inches
4. the height of your stack of firewood in feet and inches
5. the depth of the stack measured in inches
6. the estimated packing ratio in a percentage

#### Results

1. the number of cords (128 cubic feet plus voids) your pile contains based on your measurements
2. the amount of solid wood and bark measured in cubic feet your pile of firewood contains
3. what you paid for solid wood and bark content
4. the amount of money you paid for the air content