Free Wood Stove Firewood calculator
Estimate how many cords of firewood you need for the heating season — enter your home area, climate, wood type, and stove efficiency to see the cords to buy and total BTU needed, updated live, as you type.
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Estimates assume properly seasoned wood (under 20% moisture). Green wood delivers 20–30% less usable heat than dry wood of the same cord volume.
Results are estimates. Consult a professional.
How the wood stove firewood calculator works
The calculator estimates your seasonal firewood need in two steps. First, it multiplies your home's heated floor area by a climate-based heat factor to get the heat demand in BTU per hour, then multiplies by your heating hours to get the total seasonal BTU requirement. Second, it converts that BTU figure into cords by dividing by the usable heat output of one cord — the cord's heat content adjusted for your stove's efficiency.
BTU content by wood species
The heat you get from a cord of firewood depends primarily on the wood's density — denser wood has more fuel per cord. Hardwoods are denser than softwoods, which is why a cord of oak contains nearly twice the heat energy of a cord of pine. But species within those groups also vary: hickory and black locust rank near the top; balsa (if you could burn it) would be near the bottom.
| Species | Type | MMBTU per cord | Relative heat |
|---|---|---|---|
| Black locust | Hardwood | 26.8 | Excellent |
| Hickory | Hardwood | 26.5 | Excellent |
| Oak (white) | Hardwood | 25.7 | Excellent |
| Black cherry | Hardwood | 22.7 | Good |
| Maple (sugar) | Hardwood | 22.7 | Good |
| Ash (white) | Hardwood | 22.0 | Good |
| Birch (yellow) | Hardwood | 21.8 | Good |
| Douglas fir | Softwood | 18.0 | Fair |
| Pine (white) | Softwood | 14.3 | Low |
| Cedar (eastern red) | Softwood | 13.0 | Low |
Million BTU per cord (air-dried, ~20% moisture). Sourced from University of Missouri Extension, "Heating with Wood" (MU Guide G5450). Actual values vary with moisture content — green wood can deliver 20–30% less heat than seasoned wood of the same species.
Wood stove efficiency explained
No wood stove delivers 100% of a cord's potential BTU to your living space. Some heat goes up the flue as hot combustion gas; some is carried in unburned particulates. Stove efficiency is the fraction of the wood's chemical energy that actually heats your home.
Classic non-certified stoves (~60%)
Older cast-iron box stoves and fireplace inserts without secondary combustion typically achieve 55–65% efficiency. They are legal to use where installed but cannot be sold new in the US under EPA 2020 rules. At 60% efficiency you need about 25% more wood than an EPA-certified stove to produce the same heat.
EPA-certified stoves (~75%)
Stoves certified under the EPA 2020 New Source Performance Standard (NSPS) must meet emission limits that effectively require secondary combustion air or catalytic combustors, pushing efficiency to 70–80%. The calculator's default of 75% is a realistic midpoint for a current EPA-certified stove.
Modern high-efficiency stoves (~80%)
Catalytic and gasification stoves can achieve 80–90% efficiency by burning the combustion gases a second time in a high-temperature secondary chamber. Scandinavian soapstone stoves and high-mass designs are common in this tier. They cost more upfront but reduce both fuel consumption and creosote accumulation.
Heating factor by climate zone
The heating factor (BTU per sq ft per hour) is the biggest variable in this calculation — it varies more between climates than between wood species. A well-insulated house in Atlanta needs about half the BTU per square foot of a similar house in Minnesota. Use the table below as a starting point; a well-insulated modern home will sit at the low end of each range, an older drafty house at the high end.
| Climate zone | Heating factor range | Example states / cities | Heating days |
|---|---|---|---|
| Mild | 25–35 BTU/ft²/hr | Southern US, Pacific Coast, Pacific NW valleys | 90–130 |
| Moderate | 35–42 BTU/ft²/hr | Mid-Atlantic, Carolinas, Pacific NW coast | 130–180 |
| Cold | 42–50 BTU/ft²/hr | Great Lakes, New England, Northern Plains | 180–230 |
| Very cold | 50–55 BTU/ft²/hr | Northern Minnesota, Maine, mountain West | 220–270 |
Heating factors are rules of thumb from residential HVAC sizing practice. Heating days are approximate calendar days with a mean temperature below 65°F (heating degree-day standard). Actual need depends on insulation, infiltration, and internal heat gains.
Why you must season firewood before burning
Freshly cut ("green") wood can be 50% water by weight. That water absorbs heat from the fire as it vaporises, dramatically reducing the useful BTU delivered to your home and dramatically increasing creosote deposition in the flue. The BTU content figures in this calculator assume properly seasoned wood at roughly 20% moisture content — the standard dried condition.
Reaching 20% moisture typically takes 6–12 months of air-drying for most softwoods and 12–24 months for dense hardwoods like oak. Kiln-dried firewood is available at a premium and reaches burning-ready moisture immediately.
- Split rounds before stacking — split wood dries four to five times faster than whole rounds because moisture escapes through the cut wood faces rather than just the bark.
- Stack off the ground on pallets or rails to allow air circulation under the pile and prevent rot and insect infestation from the soil.
- Cover the top only — covering the sides traps moisture. Leave the ends open to the wind.
- Test with a moisture meter (under $20) before burning. Aim for under 20%; under 15% is excellent.
A worked example: 1,500 sq ft home in a moderate climate
David heats a 1,500 sq ft home in Virginia with an EPA-certified wood stove (75% efficiency). He burns hardwood (oak and ash, 22 million BTU per cord) for about 150 days a year, averaging 8 hours a day. His house sits in a moderate climate — he uses a heating factor of 35 BTU per sq ft per hour.
Step 1 — Calculate heat load
1,500 × 35 = 52,500 BTU/hr required to keep the home warm.
Step 2 — Calculate heating hours
150 days × 8 hours = 1,200 hours of heating per year.
Step 3 — Calculate total BTU
52,500 × 1,200 = 63,000,000 BTU = 63 million BTU per season.
Step 4 — Convert to cords
Usable heat per cord: 22 × 0.75 = 16.5 MMBTU. Cords: 63 ÷ 16.5 = 3.82 cords. Rounded up to the nearest 0.5: buy 4 cords.
Tips for buying and storing firewood
Firewood pricing varies enormously by region, species, and whether you're buying green wood to season yourself or ready-to-burn split and seasoned cord wood. A few key points to avoid overpaying or getting less than you paid for:
- Always buy in full cords, not "truck loads." A pickup truckload is not a legal unit of measure. Ask the seller to state the dimensions of the stacked cord — it should total 128 cubic feet.
- Inspect before buying. Properly seasoned wood has cracked end-grain, feels light for its size, and makes a hollow "clunk" rather than a dull thud when two pieces are knocked together.
- Order in late winter or early spring for the following heating season — prices are lowest off-season and you have time to season green wood yourself if necessary.
- Stack and cover promptly. Wood left in a pile on the ground will absorb moisture and begin to rot within one season.
- Buy one extra half-cord as a buffer. Running short in February forces you to buy at peak-season prices.
Wood heating terms
Frequently asked questions about the free Wood Stove Firewood calculator
About this Wood Stove Firewood calculator
This wood stove firewood calculator runs entirely in your browser — none of your inputs are sent anywhere, and the cord estimate updates live as you adjust the sliders. It uses a BTU-based method that accounts for your climate, heating hours, wood species, and stove efficiency.
It is part of our home & garden calculators, alongside the cord of wood and other heating tools. Browse the full calculator library for more home planning calculators.