The Science of Firewood Heat Output
If you rely on a wood stove or fireplace to heat your home during the winter, not all wood is created equal. Buying "three cords of wood" doesn't guarantee you will stay warm if the wood is a low-density, fast-burning species.
The heat output of firewood is measured in British Thermal Units (BTUs), and the total heat you get depends entirely on the density of the wood you are burning.
Hardwood vs. Softwood
- Hardwoods (Oak, Hickory, Maple): These trees grow very slowly, resulting in incredibly dense wood. Because there is more physical mass per cubic inch, a standard cord of seasoned Oak can produce roughly 24 to 28 Million BTUs of heat. It burns slowly, creating a bed of hot coals that radiates heat for hours.
- Softwoods (Pine, Fir, Spruce): These trees grow rapidly and have low density. A standard cord of Pine only produces about 14 to 15 Million BTUs. It ignites quickly and burns very hot, but the fire will die out rapidly and leave very few coals.
This calculator looks at your total cords and the percentage mix of hardwood vs. softwood to give you the true, absolute heat value of your winter supply.
The Mathematical Formula
To calculate this scenario accurately, the following formula is applied:
Where:
=
Total Heat Energy (Millions of BTUs)C=
Total Cords of Wood=
Percentage of Hardwood