Firewood BTU Calculator
Compare the heat energy of a cord of firewood by species and see its equivalent in heating oil and natural gas.
How it works
Gross MMBTU = species BTU per cord × cords · Useful = gross × efficiency ÷ 100 · Oil gallons = useful BTU ÷ 138,500 · Therms = useful BTU ÷ 100,000
A cord of seasoned hardwood packs a surprising amount of energy — dense species like hickory and oak deliver far more heat per cord than softwoods like pine, which is why they are prized for wood heat. Actual delivered heat depends on your appliance: an open fireplace may waste most of it, while a modern wood stove converts around 70–80%. Converting to heating-oil gallons and natural-gas therms makes it easy to compare the value of a cord against your other fuel bills.
Worked example
One cord of red oak is 24.6 MMBTU gross. At 70% stove efficiency the useful heat is 17.2 MMBTU, which matches about 17.2 million ÷ 138,500 = 124 gallons of heating oil or 172 therms of natural gas.
Frequently asked questions
Why is hardwood worth more than softwood?
Denser hardwoods pack more mass — and therefore more energy — into the same cord volume. Hickory or oak can deliver over 50% more heat per cord than pine, so even at a higher price per cord they often cost less per unit of heat.
Does moisture content matter?
Enormously. Green, unseasoned wood can be 50% water, and burning off that water steals heat and creates creosote. These figures assume properly seasoned wood at around 20% moisture; wet wood delivers far less usable heat.
What efficiency should I use?
An open fireplace is often only 10–20% efficient, an older wood stove around 50–60%, and a modern EPA-certified stove or insert 70–80%. Enter the figure for your appliance to get realistic useful heat.
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This calculator is for educational purposes. Double-check important results before acting on them.