An air dried cord of firewood has about 20% moisture still remaining in it (this is often referred to as “seasoned” firewood). As every wood species weighs differently, breaking down firewood by the pound to conclude the amount of fuel value it contains makes comparing various wood types easier.

A bone dry pound of wood represents 8600 BTUs (this would be as if you could get the wood to zero percent moisture). Since, in the real world, an air dried cord is about 20% moisture, this is taken into consideration when calculating BTUs. Therefore, air dried (20% moisture) hardwood firewood contains about 7,000 BTUs per pound with Douglas Fir containing 7360 BTUs per pound and White Pine containing 7200 BTUs per pound. (Why are Douglas Fir and White Pine different? The answer is because they have inflammable resins in the wood that the others do not).

By knowing the type of wood you are burning, you can calculate the number of anticipated BTUs you will get from the wood. However, there is one more important factor to consider in how much fuel value you will get from your firewood. That factor is the efficiency of the wood stove burning it. For example, if you have a wood stove that is only 50% efficient and you are burning white oak, you can anticipate 15.4 million BTU’s from the wood. If your wood stove is 60% efficient, you increase your BTUs to 18.5 million which is a 20% increase in BTUs for raising efficiency 10%.

Knowing all this information is helpful when determining whether wood is your best choice for heat (over oil, gas, or electric) and for determining whether upgrading to a more efficient stove is cost effective.