Estimate how many cords of firewood you need for a heating season from home size, climate, insulation and stove type, or from your burn rate.
Firewood Usage Formula
- Cords = full cords of firewood used per heating season (1 cord = 128 cubic feet of stacked wood)
- A = heated floor area in square feet
- HDD = heating degree days for your location and heating period, using a consistent 65°F (about 18.3°C) base; the calculator converts °C·day to °F·day
- I = supplied building-specific heat-loss factor in Btu per square foot per °F·day; I = 24 × UA / A when UA is the whole-building heat-loss coefficient in Btu/h·°F
- S = share of your heating done with wood, as a decimal (1.0 if wood is your only heat)
- B = supplied wood energy in Btu per full cord at the actual moisture level; enter million Btu per cord in the widget
- E = supplied appliance overall efficiency as a decimal; use the same HHV or LHV energy basis as B
The seasonal mode multiplies area, degree days, your building-specific heat-loss factor and the wood-heating share, then divides by delivered heat per cord. Climate, insulation, wood type and appliance start at typical values that you can replace with Custom values; no additional moisture penalty is applied. Use a compatible wood-energy and efficiency basis to avoid double counting losses. This is a simplified planning heat budget, not equipment sizing. The burn rate mode skips the heat model and instead multiplies the wood you actually burn per day by the number of heating days:
- R = wood burned per day in cubic feet
- D = heating days in the season
The supply-duration mode divides stacked volume by daily usage. Months are defined here as 30.4 days, and a week is seven days. Optional fields in the seasonal and burn-rate modes add your chosen reserve, USD cost and piece-count estimate; blank reserve adds none, blank wood share uses 100%, and blank price or pieces omits that output.
Heat Content by Species and Fuel Cost Comparison
The following energy figures are illustrative planning assumptions retained from the original article, not guaranteed species or seller specifications. Stacking, density and moisture change energy per cord. The widget’s wood-type presets use these values, or choose Custom wood energy. The last column divides the assumed white-oak value of 25.7 by each row’s assumed value; it is not a comparison of appliance-delivered heat.
| Species | Million BTU per cord | Cords to equal 1 cord of white oak |
|---|---|---|
| Hickory | 27.7 | 0.93 |
| Black locust | 26.8 | 0.96 |
| White oak | 25.7 | 1.00 |
| Red oak | 24.6 | 1.04 |
| Sugar maple | 24.0 | 1.07 |
| Ash | 23.6 | 1.09 |
| Mixed hardwood | 22.0 | 1.17 |
| Douglas fir | 20.6 | 1.25 |
| Pine | 16.2 | 1.59 |
The comparison below is an illustrative price-and-efficiency scenario, not current market data or a recommendation. Firewood rows assume 22 million Btu per full cord and the stated 75% efficiency; other rows use the displayed fuel price and efficiency. Use local prices and compatible tested energy/efficiency figures for your own comparison.
| Heat source | Assumed price | Efficiency | Cost per million BTU delivered |
|---|---|---|---|
| Firewood, self-cut | $75/cord (permit, fuel, gear) | 75% | about $4.50 |
| Firewood, delivered hardwood | $300/cord | 75% | about $18 |
| Heat pump | $0.16/kWh | COP 3.0 | about $16 |
| Natural gas furnace | $1.50/therm | 95% | about $16 |
| Heating oil | $3.60/gal | 85% | about $31 |
| Propane | $2.80/gal | 92% | about $33 |
| Electric baseboard | $0.16/kWh | 100% | about $47 |
Prices, labor, equipment, maintenance, fuel moisture and actual appliance performance can change this ranking. These examples do not establish the cheapest heat source for a particular home.
Firewood Usage Example Problems
Example 1: Seasonal usage. For an illustrative heat budget, enter 1,800 ft² and choose Cold (6,000 °F·day), Average insulation (5 Btu/ft² per °F·day), Red oak (24.6 million Btu per full cord) and an EPA-certified stove (75%).
Total heat required = 1,800 x 6,000 x 5 = 54,000,000 BTU. Usable heat per cord = 24,600,000 x 0.75 = 18,450,000 BTU. Cords = 54,000,000 / 18,450,000 = 2.93 full cords, or about 8.8 face cords. An optional reserve of about 19.6% would increase this example to about 3.5 full cords; choose a reserve appropriate to your circumstances.
Example 2: How long will the pile last? You have 3 full cords stacked (3 x 128 = 384 cubic feet) and burn about 2.5 cubic feet per day.
Days = 384 / 2.5 = 153.6, so the supply lasts about 154 days, roughly 22 weeks or 5 months. Six 30.4-day months at the same rate would use 3.5625 full cords, about 0.5625 cord more than this supply, before any chosen reserve.
FAQ
What is the difference between a full cord and a face cord?
A full cord is a stack 4 feet high, 4 feet deep, and 8 feet long, or 128 cubic feet. A face cord is the same 4 by 8 foot face but only one log deep. With a 4 by 8 foot face and 16 inch logs, that particular stack is 128/3 ft³, one third of a full cord. Other log lengths change the volume. The calculator labels this assumption explicitly; “face cord” alone is not a standardized volume or an approved sales unit under NIST’s model regulation. Confirm actual stack dimensions and local rules.
How much does burning green wood increase usage?
Wet wood reduces useful heat and can increase smoke and creosote. There is no universal 0.6 or 0.85 moisture multiplier in this calculator. Use wood energy and appliance efficiency appropriate to the actual fuel and the same energy basis. EPA advises burning wood below 20% moisture; drying time varies, so check a freshly split face with a moisture meter rather than relying only on elapsed months.
How many cords does a typical home use per winter?
Floor area alone cannot establish seasonal cord use. Use your measured burn history where possible, or a building-specific heat-loss factor, local degree days and applicable energy/efficiency inputs. The calculator does not supply a universal household range.
