Firewood Calculator
Estimate how many cords of firewood you need for a heating season from your home's area and a seasonal BTU-per-square-foot factor.
How this calculator works
Heating a home for a season takes a certain amount of total heat energy, which scales with the home’s square footage and a seasonal BTU-per-square-foot factor for your climate and insulation level. Once you know that total energy requirement, dividing by the heat content of a cord of seasoned hardwood tells you roughly how many cords to plan for.
Formula: Total heat needed for the season (BTU) = home area × BTU per sq ft for the season. Cords needed = total BTU ÷ BTU per cord (about 20 million BTU per cord of seasoned hardwood).
Worked example
A 2,000 sq ft home with a seasonal factor of 15,000 BTU/sq ft:
- Total BTU = 2,000 × 15,000 = 30,000,000 BTU
- Cords = 30,000,000 ÷ 20,000,000 = 1.5 cords
Notes
This estimate assumes well-seasoned hardwood such as oak or maple, which burns hotter and longer than softwood — using softwood instead will require more cords for the same heat output.
A colder climate or a drafty, older, poorly insulated home increases the amount of heat that escapes, which raises the BTU-per-sq-ft factor you should use for that home compared to a newer, tighter-built house of the same size.
How to use
Enter your home’s square footage and a seasonal BTU-per-square-foot factor that reflects your climate and insulation level. The calculator divides your total seasonal heat need by the heat content of a cord to give you a rough number of cords to plan for the season.
A rough seasonal planning estimate. Actual firewood use depends on climate, insulation, wood species, and how much of your heat comes from wood vs. another source.
Frequently asked questions
Where does the BTU-per-square-foot figure come from?
It's a seasonal heating factor that estimates how much total heat energy your home needs to stay warm through a heating season, based on its size. This figure varies by climate, insulation quality, and home age, so it's an input you set based on your region and home rather than a fixed constant.
Why is a cord measured in BTUs of firewood?
A cord of well-seasoned hardwood contains a fairly consistent amount of stored heat energy, commonly figured at around 20 million BTU. Dividing your home's total seasonal heat need by that per-cord figure converts an energy requirement into a number of cords you can actually order or stack.
Does wood species change how many cords I need?
Yes. Dense hardwoods like oak and maple pack more heat energy per cord than lighter softwoods like pine, so a cord of softwood generally won't go as far. This calculator assumes seasoned hardwood; if you're burning mostly softwood, expect to need more cords for the same heat output.
Why would a drafty or older home need more cords than this estimate?
Heat loss through walls, windows, and gaps increases the total energy needed to keep a home warm, which raises the effective BTU-per-square-foot figure for that home. A drafty older home or one in a colder climate should use a higher BTU-per-square-foot input than a newer, well-insulated home of the same size.
Estimates only. Verify quantities with your supplier before purchasing.