Firewood Cord Volume, Weight & Seasoning BTU Heat Output Sizer
A cord of green oak and a cord of seasoned oak look identical stacked in the yard, but burning wet wood wastes a huge share of its heat energy boiling off trapped moisture and builds dangerous creosote in the chimney. This calculator converts stack dimensions into cords and adjusts BTU output for species and moisture content.
This 0.33-cord stack of oak yields approximately 6.0 million BTU of usable heat.
| Metric | Value |
|---|---|
| Stack dimensions | 8.0 × 1.33 × 4.0 ft |
| Total cubic feet | 43 |
| Full cords (128 cu ft) | 0.33 |
| Face cords (÷3) | 1.00 |
| Species dry BTU/cord | 24.0M |
| Moisture content | 20% |
| Available BTU after moisture loss | 6.0M BTU |
- 1.
TotalCords = (Length × Width × Height) / 128 - 2.
AvailableBTU = SpeciesDryBTU × (1 − Moisture% × 1.25) × TotalCords
How to Use This Calculator
1. Enter your details
Use the labelled fields and units that match your situation.
2. Calculate instantly
The result, visual comparison, and working update as values change.
3. Review your result
Check assumptions, then copy, print, or share the calculation.
Formula & step-by-step maths
- SpeciesDryBTU
- Million BTU per full cord at <20% moisture
- Moisture%
- Fraction of wood weight that is water
What is a full cord vs a face cord?
A full cord is a stack measuring 4×4×8 feet, or 128 cubic feet of wood and air space. A face cord (or 'rick') is only as deep as one log length — typically 16 inches — so it takes three face cords of 16-inch logs to equal one full cord.
Why moisture destroys usable heat
Green wood can be 50% water by weight; a huge share of the fire's energy goes into evaporating that water instead of heating your home. Fully seasoned wood under 20% moisture burns hotter, cleaner, and more efficiently.
Species BTU differences
Dense hardwoods like hickory and oak pack far more energy per cord than softwoods like pine — hickory burns nearly twice as hot per cord as pine, though pine seasons and ignites faster, making it useful for kindling and shoulder-season fires.
Creosote and chimney fire risk
Burning wood above 25% moisture produces cooler, smokier fires that deposit more creosote in the flue. Regular creosote buildup from wet wood is a leading cause of residential chimney fires — always season wood 6-12 months before burning.
Dry BTU output per full cord by species
| Species | Million BTU/cord (dry) | Seasoning time |
|---|---|---|
| Hickory | 27.7 | 12 months |
| Oak | 24.0 | 12-24 months |
| Ash | 23.6 | 6-12 months |
| Birch | 20.8 | 6-12 months |
| Pine | 15.0 | 6-9 months |
| Maple | 22.0 | 9-12 months |
Frequently Asked Questions
Three worked examples
Same engine, three different starting points — useful if you want to see how sensitive the answer is before you type your own numbers in.
Example 1: stack length 6.24 ft, wood species "Oak (24 million BTU/cord dry)"
On the lower / more conservative end. This 0.26-cord stack of oak yields approximately 4.7 million BTU of usable heat.
Example 2: stack length 8 ft, wood species "Oak (24 million BTU/cord dry)"
A typical middle-of-the-road setup. This 0.33-cord stack of oak yields approximately 6.0 million BTU of usable heat.
Example 3: stack length 10.4 ft, wood species "Hickory (27.7 million BTU/cord dry)"
On the higher / more demanding end. This 0.43-cord stack of hickory yields approximately 9.0 million BTU of usable heat.
Quick answers about the Firewood Cord & BTU
What exactly does the Firewood Cord & BTU work out?
A cord of green oak and a cord of seasoned oak look identical stacked in the yard, but burning wet wood wastes a huge share of its heat energy boiling off trapped moisture and builds dangerous creosote in the chimney. You enter stack length, stack width (log length), stack height and wood species (plus 1 more optional details) and the result panel updates straight away, so you can compare two or three versions of the same question in a few seconds.
What do I need before I start?
Only 5 fields: stack length, stack width (log length), stack height, wood species and moisture content. Nothing else is needed and nothing is stored.
What is a full cord vs a face cord?
A full cord is a stack measuring 4×4×8 feet, or 128 cubic feet of wood and air space. The same maths runs inside this page, so hand-checking the result on paper gives you the identical figure.
Why do two calculators give me different answers for firewood Cord & BTU?
Green wood can be 50% water by weight; a huge share of the fire's energy goes into evaporating that water instead of heating your home. Different sites pick different assumptions, so always check which method a calculator states before you trust the gap between two numbers.
What does the "Dry BTU output per full cord by species" table on this page tell me?
It is the reference range this tool works against — 6 rows from "Hickory" (27.7) up to "Maple" (22.0). Use it to sanity-check whether the number you just calculated sits where you expected it to.
Which wood species should I pick?
The dropdown offers 5 choices — Oak (24 million BTU/cord dry), Hickory (27.7 million BTU/cord dry), Ash (23.6 million BTU/cord dry), Pine (15 million BTU/cord dry) and Birch (20.8 million BTU/cord dry). Pick the one that matches your real situation rather than the one you would like to be true; wood species usually moves the final figure more than any other single input, so it is worth running it twice with the option above and below your guess.
Do I have to press a button or reload the page to see the result?
No. Firewood Cord & BTU runs completely inside your browser, so the moment you change a value the cards recalculate — there is no submit step, no page reload and no waiting for a server round trip. That also means it keeps working on a weak or intermittent mobile connection.
Is it free, and do you keep what I type?
It is free with no sign-up, no app install and no usage limit. Nothing you enter into Firewood Cord & BTU leaves your device — the calculation is JavaScript running locally, so there is no upload of your figures to DrHint or anyone else.
Can I use it on a phone?
Yes — the layout stacks to a single column on small screens and the number fields open the numeric keypad on both Android and iOS. Many people bookmark this page or add it to their home screen and re-open it whenever the question comes up.
Anything to be careful about with the result?
A face cord stacked 4 ft high, 16 in deep, 8 ft long is one-third of a full cord — you'd need three such stacks side by side to equal one full 128-cu-ft cord. Treat the output as a well-grounded estimate for planning, not as a professional, legal or medical decision on its own.
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