Firewood Volume Calculator
Calculate how many cords of firewood you need for the heating season based on house size, insulation, and stove efficiency.
About this calculator
This calculator estimates a season's firewood need by first computing how many BTUs your house actually requires to stay warm, then converting that heat demand into cords of wood after accounting for how efficiently your stove burns it. The BTU requirement multiplies house square footage by heating degree days (a measure of how cold and how long your winter is) by a per-square-foot factor set by insulation quality — 10 BTU/sq ft/HDD for a poorly insulated older home, 7 for average construction, and 4.5 for a tight, well-insulated house — so the same house in the same climate can need more than double the wood depending on insulation alone. Any supplemental heat source you enter (propane, electric, etc.) proportionally reduces the load the wood stove needs to cover before the cord calculation runs.
On the supply side, one cord of mixed hardwood is assumed to hold about 20 million BTU, and your stove's rated efficiency percentage determines how much of that actually reaches the room — an EPA-certified stove around 70-80% efficient extracts far more usable heat per cord than an open fireplace at 10-20%. Logs to Process assumes roughly 100 logs (8-inch diameter, 16 inches long) make up a cord, and Cutting/Splitting Days assumes a full day of chainsaw-and-splitter work processes one cord, both rough rules of thumb rather than precise figures. Cost Estimate uses a flat $250/cord — check local firewood prices, which vary widely by region and wood species.
Inputs
Results
Cords Needed
3.6
Logs to Process
360
How to Use This Calculator
- Enter House Sq Ft and select Insulation Level (poor, average, or good) to estimate the home's heat loss.
- Look up your Heating Degree Days from NOAA climate data for your location and enter the value.
- Enter Wood Stove Efficiency (%) — EPA-certified stoves are typically 70–80%; older stoves may be 50–60%.
- Set Supplemental Heat (%) if wood is not your only heat source — this reduces the firewood requirement proportionally.
- Review Cords Needed (one cord = 128 cu ft) and Cost Estimate to plan your wood-buying or cutting season.
- Use Logs to Process and Cutting/Splitting Days to schedule your firewood preparation before winter.
How the result changes with House Size
| House Size | Cords Needed | Logs to Process |
|---|---|---|
| 750 | 1.8 | 180 |
| 1,125 | 2.7 | 270 |
| 2,250 | 5.4 | 540 |
| 3,750 | 9 | 900 |
What each input means
- House Size
- Heated floor area of your home.
- Insulation Level
- Quality of your home's insulation and air sealing.
- Heating Degree Days
- Annual heating degree days for your location (check local climate data).
- Stove Efficiency
- EPA-rated stove efficiency (modern stoves: 70-80%, open fireplace: 10-20%).
- Supplemental Heat
- Percentage of heating provided by other sources (propane, electric, etc.).
What each result means
- Cords Needed
- Cords of firewood for the heating season (128 cu ft per cord).
- Cost Estimate
- Estimated cost at $250 per cord (purchased).
- BTU Required
- Total BTU needed from wood heat.
- Logs to Process
- Approximate number of logs to cut and split.
- Cutting/Splitting Days
- Full days of work to process the firewood.
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersHouse Size = 1500, Insulation Level = 2, Heating Degree Days = 6000, Stove Efficiency = 70 = 5 input(s) provided
- Calculate Cords NeededCords Needed3.6 = 3.6
- Calculate Logs to ProcessLogs to Process360 = 360
- Calculate Cost EstimateCost Estimate900 = $900
- Calculate BTU RequiredBTU Required50400000 = 50400000
Engine last updated . Checked against 2 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
Why does insulation level change the wood requirement so much?
Insulation sets the BTU-per-square-foot-per-heating-degree-day factor: 10 for a poorly insulated older home, 7 for average construction, and 4.5 for a tight, well-insulated house. Since that factor multiplies directly into total seasonal BTU need, a poorly insulated home can require more than double the firewood of a well-sealed home of the same size in the same climate, even before stove efficiency is considered.
How does entering a Supplemental Heat percentage change Cords Needed?
The calculator first computes total seasonal BTU demand from house size, insulation, and heating degree days, then multiplies that by (1 minus your Supplemental Heat percentage) before converting to cords. So if propane or electric heat is covering 20% of your load, the wood stove only needs to supply the remaining 80%, and Cords Needed drops proportionally.
Why does Stove Efficiency matter so much to the final cord count?
One cord of mixed hardwood is assumed to hold about 20 million BTU, but Stove Efficiency determines how much of that actually heats the room versus escaping up the chimney. An EPA-certified stove around 70-80% efficient extracts far more usable heat per cord than an open fireplace at 10-20%, meaning a fireplace can require three to four times as much wood to deliver the same warmth.
How accurate are Logs to Process and Cutting/Splitting Days?
Both are rough rules of thumb, not precise figures: about 100 logs at 8 inches diameter and 16 inches long per cord, and roughly one full day of chainsaw-and-splitter work per cord. Actual counts vary with log diameter, wood species density, and your equipment and experience, so use these as scheduling estimates rather than exact targets.
Why is Cost Estimate based on a flat $250 per cord?
That figure is a general placeholder rather than a regional price — firewood costs vary widely by species, seasoning, local supply, and delivery distance, with mixed hardwood often running well above or below $250/cord depending on where you live. Swap in your local supplier's actual price for a meaningful cost projection.
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