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Firewood Cost Per Heat Calculator

Enter cord price, stove efficiency and wood type to find your true cost per BTU.

Result

How it is calculated

The tool looks up the heat content of one cord of seasoned wood in millions of BTU (MMBtu): oak 24.0, maple 24.0, ash 23.6, birch 20.8, fir 20.7 and pine 15.9. Then usable = MMBtu per cord × efficiency ÷ 100 and cost per MMBtu = price per cord ÷ usable. Cost per single BTU is that figure divided by 1,000,000. Price is per cord in dollars, and efficiency is the percentage of the wood's heat your stove delivers into the room. Efficiency must be above zero. The built-in table is fixed: a wood type not in the list, for example hickory, is silently priced as oak. The tool does not check for efficiency above 100%, and it assumes dry, seasoned wood, because wet wood delivers less heat per cord.

Worked example

Oak is offered at 300 per cord and the stove is 70% efficient. A cord of oak holds 24.0 MMBtu, so the usable heat is 24 × 70 ÷ 100 = 16.80 MMBtu. The cost is 300 ÷ 16.80 = $17.86 per million BTU, or $0.00001786 per BTU. Running the same numbers for pine at 300 gives 15.9 × 0.70 = 11.13 MMBtu and $26.95 per MMBtu, so pine would need a much lower price per cord to beat oak.

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Common mistakes

  • Entering the stove efficiency as a fraction such as 0.7 instead of 70; the cost then comes out 100 times too high.
  • Entering a price per face cord or per truckload; the tool assumes a full cord, so convert the price first.
  • Choosing a species that is not in the menu, such as hickory, and expecting a different figure; it is treated as oak.
  • Comparing species at the same price per cord and assuming equal heat; the same money buys about a third less usable heat in pine than in oak.
  • Applying the result to green or wet wood; the table values are for seasoned wood, and wet wood also burns less efficiently.

About this calculator

Not all firewood delivers the same heat per dollar. Wood species differ widely in energy density — a full cord (128 cubic feet stacked) of dense hardwood like oak or maple yields roughly 24 million BTU (ash about 23.6, birch about 20.8), while a cord of a lighter softwood like pine yields closer to 16 million BTU — so comparing raw cord prices alone can be misleading. This calculator divides the cord price by its species' BTU content and then by your stove's efficiency rating (a modern EPA-certified stove might run 65–75% efficient, versus 40–50% for an open fireplace) to find the true delivered cost per million BTU.

The efficiency factor matters as much as the wood itself: burning cheap, low-density wood in an inefficient fireplace can end up costing more per usable BTU than premium hardwood burned in a high-efficiency stove. Homeowners heating with wood, firewood sellers, and off-grid cabin owners use this comparison to decide which species and equipment combination actually delivers the cheapest heat over a winter.

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Comments (1)

  • Editorial team

    The dollar figure is per usable million BTU, after the stove's efficiency, which makes it easy to put next to other fuels. Convert a gas bill to the same basis (one therm is 0.1 MMBtu) and divide by your furnace's efficiency before comparing. Efficiency can swing the answer more than species: oak at 300 per cord costs 17.86 per MMBtu in a 70% stove but 31.25 in a 40% fireplace. What stove or fireplace are you burning in?

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