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Wood Stove Heating Calculator

Enter your heated area, seasonal heating hours, and stove efficiency.

How it is calculated

The tool assumes a fixed heating load of 30 BTU per square foot per hour while the stove runs. Seasonal demand is demand (BTU) = area × 30 × hours, with area in square feet and hours as the total hours of heating in the season. It then assumes one cord of firewood holds 20,000,000 BTU (20 MMBTU) and that only the stove's efficiency share reaches the room: cords = demand / (20,000,000 × efficiency / 100). The demand is also shown in million BTU, along with the average load, area × 30, in BTU per hour.

Both the 30 BTU and the 20 MMBTU are fixed in the tool. They do not change with climate, insulation, wind or wood species, so the result is a rule-of-thumb average for a typical home, not a heat-loss calculation. Efficiency is entered as a percent from above 0 to 100; area and hours must be above zero.

Worked example

A 1200 square foot house is heated for 1800 hours in the season by a stove with 75 % efficiency. Demand: 1200 × 30 × 1800 = 64,800,000 BTU, or 64.8 MMBTU. The average load is 1200 × 30 = 36,000 BTU/hr. Usable heat per cord: 20,000,000 × 0.75 = 15,000,000 BTU. Cords: 64,800,000 / 15,000,000 = 4.32, shown as 4.3 cords. At 50 % efficiency the same house would need 6.5 cords.

Try this example →

Common mistakes

  • Typing the efficiency as 0.75. The field is a percent, so 0.75 is read as 0.75 % and the result jumps to 432 cords. Enter 75.
  • Entering the area in square metres. The load is per square foot, so multiply square metres by about 10.76 first.
  • Entering the hours as days or as hours per day. The field is the total hours of heating across the whole season (for example 10 hours a day over 180 days is 1800).
  • Treating the cord count as exact. The tool uses a flat 30 BTU/sq ft/hr and 20 MMBTU per cord, so a poorly insulated house or a low-energy wood will need more than shown.
  • Confusing a full cord with a face cord or a truckload. The tool counts full cords (128 cubic feet); a face cord is only a fraction of that, so convert before comparing with a seller's quote.

About this calculator

Firewood is typically bought and stacked by the cord — a stack 4 feet high, 4 feet deep, and 8 feet long (128 cubic feet). This calculator estimates how many cords a wood stove will burn through in a heating season by combining the area being heated, the number of hours the stove runs, and the stove's efficiency rating, since less-efficient stoves need more fuel to deliver the same warmth.

Homeowners who heat with wood, especially in rural or off-grid settings, use this kind of estimate to plan how much wood to buy or split before winter and to budget the cost against other heating fuels. It's also useful when comparing an old, inefficient stove against a newer EPA-certified model, since a jump from roughly 50% to 75%+ efficiency can noticeably cut the cords needed per season.

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Comments (1)

  • Editorial team

    Check the unit your wood is sold in. The result is in full cords, 128 cubic feet each, while firewood is often sold by the face cord, commonly only a third or so of that. Buying 4.3 face cords would leave you well short of 4.3 full cords. The 30 BTU and 20 MMBTU figures are fixed, so treat it as a planning range. Which wood do you burn, and how does the number compare with what you stack each winter?

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