Firewood BTU Calculator
Not all firewood is created equal — a cord of hickory delivers nearly double the heat of cottonwood. Select your wood species, enter cords and local pricing to compare BTU output, cost efficiency, and heating fuel equivalents. Make informed firewood purchasing decisions.
BTU Calculator
Understanding Firewood BTU Ratings
BTU (British Thermal Unit) is the standard measure of heat energy. When comparing firewood, BTU per cord tells you how much heat a standard 128 cubic-foot stack will produce when burned. Dense hardwoods pack more wood fiber per cubic foot, which translates directly to more available energy. This is why a cord of hickory weighing 4,400 lbs produces 30.6 million BTU, while a cord of cottonwood at 2,100 lbs delivers only 15.8 million BTU.
Cost Efficiency Formula
Cost per Million BTU = Price per Cord ÷ (BTU per Cord ÷ 1,000,000)
Heating Oil Equivalent = Total BTU ÷ 138,500 BTU/gallon
Compare your firewood cost per MBTU against other fuels: natural gas (~$10/MBTU), electricity (~$30/MBTU), propane (~$20/MBTU), heating oil (~$25/MBTU). Firewood typically costs $5-12/MBTU, making it the most economical heating fuel in most regions.
Real-World Example
Heating a 2,000 sq ft home in New England with white oak at $275/cord:
- Seasonal need: ~4 cords
- Total BTU: 4 × 29.1M = 116.4 million BTU
- Total cost: 4 × $275 = $1,100
- Cost per MBTU: $275 ÷ 29.1 = $9.45/MBTU
- Heating oil equivalent: 116.4M ÷ 138,500 = 840 gallons
- At $4.00/gal oil: $3,360 — saving $2,260 with wood
Firewood BTU Comparison Table
| Wood Species | BTU/Cord (M) | Weight/Cord | Split Ease | Season Time |
|---|---|---|---|---|
| Oak (White) | 29.1M | 4,200 lbs | Medium | 12 months |
| Oak (Red) | 27.3M | 3,900 lbs | Medium | 12 months |
| Hickory | 30.6M | 4,400 lbs | Difficult | 12 months |
| Hard Maple | 29.0M | 3,900 lbs | Medium | 12 months |
| Ash | 24.0M | 3,400 lbs | Easy | 6 months |
| Birch | 23.4M | 3,300 lbs | Easy | 6 months |
| Cherry | 20.4M | 2,900 lbs | Easy | 6 months |
| Pine (Yellow) | 22.3M | 2,600 lbs | Easy | 6 months |
| Douglas Fir | 26.5M | 3,000 lbs | Easy | 6 months |
| Elm (American) | 24.5M | 3,600 lbs | Very Difficult | 12 months |
| Walnut (Black) | 22.2M | 3,200 lbs | Easy | 6 months |
| Cottonwood | 15.8M | 2,100 lbs | Easy | 6 months |
Common Firewood Mistakes
- Burning unseasoned (green) wood. Green wood has 40-50% moisture. Half the energy goes to evaporating water instead of heating your home, and it creates dangerous creosote buildup.
- Buying by the "truckload" instead of the cord. A pickup truck bed holds 1/3 to 1/2 cord depending on size. Always buy by the cord for fair comparison.
- Ignoring species when comparing prices. A $200 cord of cottonwood is more expensive per BTU than a $300 cord of hickory. Always compare cost per million BTU.
- Stacking against the house. Stack firewood at least 20 feet from your home to prevent termites, carpenter ants, and mice from migrating into your structure.
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Frequently Asked Questions
What wood has the highest BTU per cord?
Osage orange tops the charts at ~32.9 million BTU per cord, followed by hickory (~30.6M), black locust (~29.3M), and white oak (~29.1M). These dense hardwoods produce the most heat per volume and burn the longest. However, availability varies by region. For most people in the eastern US, oak and hickory are the best combination of high BTU, availability, and reasonable price.
How much firewood do I need for a winter?
The average home using wood as a primary heat source burns 3-5 cords per winter season (October-April) in northern climates. As supplemental heat (evening fires on weekends), 1-2 cords is typical. Climate zone, home insulation, stove efficiency, and wood species all affect consumption. A well-insulated 2,000 sq ft home with a modern EPA-certified stove in Zone 5 might use 3 cords of oak.
What is a cord of firewood?
A cord is 128 cubic feet of stacked firewood, typically measured as 4 feet high × 8 feet long × 4 feet deep (the length of the logs). A "face cord" (or "rick") is only 4×8 feet × the length of the individual pieces (usually 16 inches), which is 1/3 of a full cord. Always clarify whether a seller means a full cord or face cord — pricing should reflect the difference.
How long does firewood need to season?
Seasoning time depends on wood species, split size, and climate. Softwoods (pine, fir) season in 6 months. Hardwoods (oak, hickory) need 12-18 months. Wood is properly seasoned when moisture content drops below 20% (measured with a $20 moisture meter). Seasoned wood has cracked ends, sounds hollow when hit together, and is noticeably lighter than green wood. Stack off the ground with air space between rows.
Is it okay to burn pine in a wood stove?
Pine is fine for burning in modern EPA-certified stoves when properly seasoned. The concern about creosote from pine is overstated when moisture content is below 20%. Pine burns fast and hot, making it excellent for kindling and shoulder-season fires. Mixing pine with hardwoods works well — use pine to get the fire established, then add oak or hickory for sustained heat. Avoid burning unseasoned (green) pine, which does produce excessive creosote.
What is the BTU of firewood?
BTU (British Thermal Unit) measures heat energy. One BTU raises one pound of water by 1°F. Firewood BTU is measured per cord (128 cubic feet). High-BTU hardwoods (hickory: 30.6M BTU/cord) produce nearly double the heat of low-BTU softwoods (cottonwood: 15.8M BTU/cord). For comparison, a gallon of heating oil contains about 138,500 BTU, so one cord of hickory equals roughly 221 gallons of heating oil.
How do I calculate the cost efficiency of firewood?
Divide the price per cord by the BTU per cord to get cost per million BTU. Example: oak at $250/cord ÷ 29.1M BTU = $8.59 per million BTU. Compare this to heating oil (~$25/MBTU), propane (~$20/MBTU), or natural gas (~$10/MBTU). Firewood is almost always the cheapest heating fuel, especially if you cut your own. Factor in stove efficiency (75-80% for modern stoves vs 100% for electric) for a fair comparison.
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