How this is calculated
Four divisions. The house sets a seasonal heat load; species and stove set the heat a stack delivers; the two give cords; the forest growth rate turns cords into acres.
Seasonal heat in BTU is degree days × 24 hours × floor area × a shell factor. Heat in a stack comes from density: specific gravity × 62.4 lb per cubic foot × 80 cubic feet of solid wood, at 8,600 BTU per oven-dry pound, times appliance efficiency.
WORKED EXAMPLE
1,800 sq ft, average shell (0.20), 5,500 degree days: 5,500 × 24 × 1,800 × 0.20 = 47.5 million BTU for the season.
Red oak, specific gravity 0.56: 0.56 × 62.4 × 80 = 2,795 dry pounds × 8,600 BTU = 24.0 million BTU gross per cord, and a certified stove at 70% delivers 16.8.
47.5 ÷ 16.8 = 2.8 cords, or 226 cubic feet of solid wood. Oak-hickory grows 44.4 cubic feet per acre-year, of which 60% is fuel: 226 ÷ 26.6 = 8.5 acres of growing ground, carrying 214 cords standing. At 70% workable, a 12 acre parcel.
The conversion chain, written out
Each unit change is a place to lose a factor of two. These are the choices made at each one.
- Growing stock only. Net annual growth of merchantable bole wood in growing-stock trees 5 inches and up, on timberland. Tops, limbs, cull stems and saplings are real firewood and sit outside that number.
- Net of mortality. Dead and dying stems are already subtracted, so standing dead wood sits outside the budget as a windfall.
- 80 cubic feet of solid wood per cord. A cord is 128 stacked cubic feet; air fills the rest. Real stacks run 70 to 90, and this is the number most worth arguing with.
- Cut the growth, keep the stock. Only the annual increment leaves.
- The usable share is a judgment. The 60% default is a working figure that you should overwrite once you know your own ground.
Why overcutting takes decades to show
Growth is the interest and the standing timber is the capital. An acre growing half a cord a year hands over half a cord a year indefinitely.
Overshooting it stays out of sight for a long time. Three cords a year off five acres of oak-hickory is close to twice what that ground puts on as burnable growth.
Those five acres carry about 126 cords standing, some 46 years of their own growth, so ten years of cutting at that rate takes roughly a tenth of the volume and leaves a wood that still looks like a wood.
Growth by forest type
From USDA Forest Service Forest Inventory and Analysis, queried 3 September 2026 on each state’s latest evaluation. Cords use the 80 cubic foot conversion above.
| Forest type group | Net growth cu ft/acre/yr | Cords per acre-year | Standing cu ft/acre | Years of growth held standing |
|---|---|---|---|---|
| Loblolly / shortleaf pine | 147.0 | 1.84 | 2,260 | 15 |
| Longleaf / slash pine | 70.6 | 0.88 | 1,490 | 21 |
| White / red / jack pine | 69.7 | 0.87 | 3,133 | 45 |
| Douglas-fir | 63.9 | 0.80 | 3,758 | 59 |
| Hemlock / Sitka spruce | 59.8 | 0.75 | 6,256 | 105 |
| Oak / pine | 59.7 | 0.75 | 1,823 | 31 |
| Oak / hickory | 44.4 | 0.56 | 2,022 | 46 |
| Oak / gum / cypress | 41.2 | 0.52 | 2,022 | 49 |
| Maple / beech / birch | 39.8 | 0.50 | 2,076 | 52 |
| California mixed conifer | 30.3 | 0.38 | 4,639 | 153 |
| Elm / ash / cottonwood | 30.3 | 0.38 | 1,522 | 50 |
| Aspen / birch | 29.1 | 0.36 | 1,299 | 45 |
| Spruce / fir | 28.3 | 0.35 | 1,259 | 44 |
| Ponderosa pine | 26.1 | 0.33 | 1,774 | 68 |
| Fir / spruce / mountain hemlock | 14.7 | 0.18 | 3,308 | 226 |
| Lodgepole pine | −6.4 | losing volume | 1,509 | — |
Every group holding more than 5 million acres of timberland; nonstocked ground is left out. Lodgepole pine is in net decline nationally, which is what beetle mortality looks like in an inventory table.
Growth by state
The same query, grouped by state.
| State | Net growth cu ft/acre/yr | Cords per acre-year | Standing cords/acre | Years of growth held standing |
|---|---|---|---|---|
| Mississippi | 111.3 | 1.39 | 26.6 | 19 |
| North Carolina | 92.3 | 1.15 | 31.5 | 27 |
| Georgia | 86.4 | 1.08 | 23.5 | 22 |
| Arkansas | 78.2 | 0.98 | 23.5 | 24 |
| Virginia | 76.5 | 0.96 | 31.7 | 33 |
| Washington | 71.2 | 0.89 | 48.7 | 55 |
| Oregon | 67.4 | 0.84 | 48.8 | 58 |
| Indiana | 63.7 | 0.80 | 36.1 | 45 |
| Tennessee | 62.4 | 0.78 | 29.2 | 37 |
| Kentucky | 54.5 | 0.68 | 27.7 | 41 |
| West Virginia | 49.8 | 0.62 | 30.5 | 49 |
| New York | 45.9 | 0.57 | 27.0 | 47 |
| New Hampshire | 45.5 | 0.57 | 29.5 | 52 |
| Wisconsin | 45.2 | 0.57 | 21.7 | 38 |
| Ohio | 43.8 | 0.55 | 27.4 | 50 |
| Massachusetts | 42.8 | 0.54 | 36.3 | 68 |
| Michigan | 42.5 | 0.53 | 25.5 | 48 |
| Vermont | 40.0 | 0.50 | 27.4 | 55 |
| Maine | 38.7 | 0.48 | 18.1 | 37 |
| Minnesota | 35.3 | 0.44 | 15.6 | 35 |
| Connecticut | 35.1 | 0.44 | 31.3 | 71 |
| Pennsylvania | 32.9 | 0.41 | 27.5 | 67 |
| Missouri | 30.6 | 0.38 | 19.0 | 50 |
| Idaho | 16.1 | 0.20 | 30.1 | 150 |
| Montana | 2.0 | 0.02 | 20.8 | 846 |
| Colorado | −17.5 | losing volume | 22.1 | — |
A Pennsylvania acre carries 67 years of its own growth, which is why a woodlot can be overcut for decades before it shows.
Europe in cubic meters per hectare
The European inventories measure the same quantity under different names: Zuwachs in Germany, production biologique in France, both in cubic meters of stem wood per hectare per year.
| Inventory | Growth m³/ha/yr | Steres per hectare-year | Standing m³/ha | Period |
|---|---|---|---|---|
| Germany, BWI 2022 (Thünen) | 9.4 | 15.0 | 335 | 2012–2022 |
| France, IGN gross production | 5.4 | 8.6 | 172 | 2014–2022 |
| France, IGN net production | 4.4 | 7.0 | 172 | 2014–2022 |
| France, Nouvelle-Aquitaine | 6.7 | 10.7 | — | 2014–2022 |
| France, Grand Est | 6.3 | 10.1 | — | 2014–2022 |
| France, Auvergne-Rhône-Alpes | 6.1 | 9.8 | — | 2014–2022 |
| France, Occitanie | 3.9 | 6.2 | — | 2014–2022 |
| France, Provence-Alpes-Côte d’Azur | 2.1 | 3.4 | — | 2014–2022 |
Both are falling. German growth is down about 16% against the 2012 inventory, which the Thünen Institute puts down to bark beetle damage in spruce and drought; French gross production slipped from 5.8 m³/ha in 2005–2013 to 5.4.
Cross-reading: 5.4 m³/ha/yr is about 77 cubic feet per acre-year, roughly Virginia woodland.
Cross-reading: 44.4 cubic feet per acre-year is about 3.1 m³/ha/yr, near the Mediterranean end of the French range.
A stere is a stacked cubic meter holding 0.625 m³ of solid wood here, the same packing fraction the firewood BTU chart uses, so the two pages describe one stack. Meter-length logs pack tighter than 33 cm billets, which is where most delivery arguments start.
Coppice against standing timber
Everything above assumes high forest: single stems, thinned, felled, replaced by seedlings. Coppice regrows from an established root system, so the cycle is 15 to 25 years rather than 60 to 100.
That buys a small-diameter, hand-workable crop on a schedule. Sweet chestnut, hazel, ash, willow and oak coppice reliably; beech is a poor coppicer and conifers other than yew do not regrow from a cut stump at all. The practical form is a rotation of blocks, one cut a season, sized off the acreage above.
The work inside a cord
A cord of seasoned red oak at 20% moisture weighs about 3,500 pounds and moves by hand three or four times: felled and bucked, split, stacked to season, carried to the stove. The saw work is the short part.
Seasoning sets the calendar. Split oak wants two summers under cover, so the woodpile stays two years ahead of the stove and a new parcel heats the house the winter after next.
From deed acres to cutting acres
Deed acres and cutting acres are different numbers. Off the top come wet ground no trailer crosses, ledge and steep faces, stream buffers, the screen near the house, and sawlog stems worth more standing than burned. On many parcels the workable ground is 50 to 70% of the total, which is why the calculator reports both.
Access moves it most: an old skid road running downhill to the house is a different asset from the same trees across a wet bottom.
What moves the answer more than the arithmetic
Species mix first. Black locust and hickory carry about a quarter more heat per cord than mixed hardwood and nearly 80% more than spruce, so identical cubic feet of growth heat very different houses.
The stove second. Going from an open fireplace to a certified stove cuts the wood needed by a factor of seven, worth more than any amount of extra land; the stove sizing guide matches output to the room.
Then the house: halving the shell factor halves the cords and the acres. If wood is one part of a wider plan, run the whole load through the off-grid house calculator first. Last comes terrain, which resists arithmetic entirely.
Quick answers
How many acres of woodland does it take to heat a house?
For an 1,800 square foot house at 5,500 degree days burning three cords in a certified stove, about 9 acres of eastern oak-hickory growing ground, or a 13 acre parcel once wet ground and keepers come off. Loblolly-shortleaf pine does it in 3. Spruce-fir and the dry western types need 14 to 27.
How many cords does one acre grow in a year?
Oak-hickory averages 44.4 cubic feet per acre-year, which is 0.56 cords. Maple-beech-birch is 0.50, spruce-fir 0.35, loblolly-shortleaf pine 1.84.
Can you cut firewood from the same woodlot forever?
Yes, provided the yearly cut stays inside the yearly growth. Past that you are drawing down standing volume, and an eastern acre holds 40 to 70 years of its own growth, so the draw-down runs for decades before the cut gets thin.
How much wood does a hectare of European forest grow?
Germany measured 9.4 m³ per hectare per year in BWI 2022. France gives 5.4 m³ gross for 2014–2022, from 2.1 in the Mediterranean regions to 6.7 in Nouvelle-Aquitaine.
How much firewood does a wood-heated home actually burn?
The 2020 Residential Energy Consumption Survey found homes heating mainly with wood burned 85.0 million BTU each, about 3.5 cords of red oak. The Midwest averaged 123.1, the South 69.2.
Sources
- US growth and standing volume. USDA Forest Service, Forest Inventory and Analysis, FIADB-API EVALIDator (database FIADB_1.9.4.00), queried 3 September 2026: average annual net growth of merchantable bole wood volume of growing-stock trees at least 5 inches d.b.h., and net volume of the same trees, each divided by timberland acres, across the 56 most recent state growth evaluations, inventory years 2022 to 2025.
- Germany. Vierte Bundeswaldinventur (BWI 2022), Thünen Institute, 2024: 9.4 m³/ha/yr, 101.5 million m³/yr, 335 m³/ha standing.
- France. IGN, 2024 National Forest Inventory, a handbook: gross production 87.9 ± 1.3 million m³/yr and 5.4 m³/ha/yr over 2014–2022, net 4.4, growing stock 172 m³/ha.
- Household wood use. US Energy Information Administration, 2020 Residential Energy Consumption Survey, table CE7.2, June 2023.
- Density and heat. USDA Forest Products Laboratory Wood Handbook specific gravities, green-volume basis; 8,600 BTU per oven-dry pound (University of Arkansas Extension FSA1091) and the 80 cubic feet of solid wood in a 128 cubic foot cord (University of Maryland Extension FS926), the same pair the firewood BTU chart runs on.
Go deeper
Size the whole house with the off-grid house calculator, then come back for the acres its heating half needs. The firewood BTU chart ranks 60 species by heat per cord and stere, and the heating degree day map supplies the climate number. For fuels side by side read wood against propane, heat pump and pellet, then walk the ground with the land buying checklist.