Free firewood BTU calculator. Enter cords of firewood and BTU per cord to find total heat energy and equivalent gallons of heating oil.
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Multiply cords by BTU per cord for total heat, then divide by 138500 BTU per gallon of heating oil. Two cords at 20 million BTU per cord give 40 million BTU, about 288.81 gallons of oil. The result is gross heat before stove efficiency, so the usable heat in the room is lower.
Total heat is cords times BTU per cord, and the heating oil equivalent divides that total by 138500, the heat in one gallon of heating oil. One cord is 128 cubic feet of stacked wood, about 85 cubic feet of solid wood once air gaps are removed. Use the BTU per cord figure for your species, or 20 million as a mixed hardwood average, and this firewood BTU calculator returns both the total heat and the oil equivalent in one step.
Competitor BTU charts agree on the ranking even when exact figures differ a little by source and moisture. Hickory leads at about 27 to 28 million BTU per cord, followed by white oak at about 25.7 million, red oak and sugar maple at about 24 million, white ash at about 23.6 million, yellow birch at about 21 to 23.6 million, black cherry at about 20 million, pine at about 15 to 17 million, and cedar at about 13 to 15 million. All of these values assume seasoned wood at roughly 20 percent moisture.
Moisture is the biggest single cause of heat loss from firewood. Green wood spends much of its heat evaporating its own water, and competitor guides warn that wet wood can lose around half of its potential heat. Season wood for 6 to 12 months, and 12 to 24 months for dense oak. Store it off the ground, covered on top but open at the sides for airflow, and check it with a moisture meter before burning.
Hardwoods are denser, so they pack more heat into a cord, burn slowly, and leave long lasting coals, which suits overnight heating. Softwoods ignite fast and burn fast, with more sparks and more creosote, so they suit kindling and shoulder season fires rather than all winter heating. A mix works well: softwood to start the fire, hardwood to hold the heat.
Two cords at 20 million BTU per cord hold 40 million BTU, equal to about 288.81 gallons of heating oil at 138500 BTU per gallon. One hundred gallons of oil hold about 13.85 million BTU, roughly two thirds of a cord of good hardwood. Remember stove efficiency: a stove at 70 percent efficiency turns 40 million BTU of wood heat into about 28 million BTU of room heat, so compare delivered heat, not gross heat, when pricing fuels.
To size a winter supply, competitor worked examples multiply home area by heating degree days and an insulation factor, then divide by heat per cord times stove efficiency. A 1500 square foot home at 6000 heating degree days, 5 BTU per square foot per heating degree day, 25 million BTU per cord, and 0.70 efficiency needs about 2.57 cords, so plan for about 2.5 to 3 cords for the season and round up. Enter your cords above to check what your own woodpile is worth in heat and in gallons of oil.
It depends on species. Dense hardwoods like hickory reach 27 to 28 million BTU per cord and oak reaches about 24 to 25.7 million, while softwoods like pine sit closer to 15 to 17 million. All figures assume seasoned wood.
Hickory and black locust top most BTU per cord charts at about 27 to 28 million BTU per cord, with white oak close behind. They burn long and hot and leave strong coals, but they need a long seasoning time.
One hundred gallons of heating oil hold about 13.85 million BTU, roughly two thirds of a cord of good hardwood at 20 million BTU per cord. Two cords at 20 million BTU per cord equal about 288.81 gallons of oil.
It is accurate for gross heat from seasoned wood with a realistic BTU per cord figure. It does not apply stove efficiency or moisture loss, so real room heat is lower. Always round up when ordering, so you do not run short midwinter.
Store wood off the ground, covered on top but open on the sides for airflow, and season it for at least 6 months to a year, longer for oak. Dry wood burns hotter, cleaner, and with less creosote than green wood.
Yes. Evaporating water inside green wood consumes heat that would otherwise warm your home, and competitor guides report losses of up to half the potential heat. Burning wet wood also builds creosote faster, so season first and burn dry.
A full cord is 128 cubic feet of stacked wood, usually a stack 4 feet high, 4 feet deep, and 8 feet long. A face cord is a single row of that stack, usually about one third of a full cord for 16 inch logs, so confirm which measure a seller is quoting before you pay.