Article — Firewood Calculator
For a 2,000 sq ft house in a moderate U.S. climate, a primary wood-stove burner at 75% efficiency burns through roughly two-and-a-half cords of hardwood across a six-month season. Step up to a cold zone and the figure climbs past three-and-a-half. Switch to softwood and add another 50% on top. The math is simple; the variables that shift it — climate, stove efficiency, wood species, moisture — are where the cord count gets won or lost.
This article walks through what a cord actually is, how seasonal demand is estimated, why a seasoned oak log delivers nearly double the heat of a green pine one, and the storage habits that decide whether your wood is ready to burn next winter.
What a cord of firewood actually is
A cord is a U.S. and Canadian legal unit for stacked firewood. The dimensions are fixed: 4 feet high, 8 feet long, 4 feet deep, totalling 128 cubic feet of wood, bark, and the unavoidable air gaps between split pieces. The standard has been on statute books since the 17th century, when colonial governments wrote it down to stop merchants selling loose "stacks" of indeterminate size.
A face cord is the part that confuses buyers. It is the same 4 by 8 foot wall, but only one log deep. For wood cut at 16 inches — the most common stove length — that face is one-third of a full cord. Three face cords of 16-inch wood equal one full cord. If the seller cuts to 24 inches, the ratio drops to one-half. Always ask what cut length is being quoted.
The cord predates the United States. The word comes from the literal cord (rope) once used to measure wood piles in 17th-century England. American colonial assemblies formalised the dimensions to prevent shortchanging — one of the earliest weights-and-measures laws in North America.
How much firewood you really need
Three numbers drive the answer: the area you actually heat, the climate that area sits in, and the efficiency of the stove burning the wood. Heated area is straightforward — measure only the rooms the stove keeps warm, not the total floor plan if you close off bedrooms or upstairs.
Climate sets the BTU demand per square foot per month. A mild winter (10–20 °F lows) runs about 20 BTU/sq ft/month; a severe winter (below −20 °F) climbs to 70 — three-and-a-half times the demand for the same house. Stove efficiency then divides into that figure: a modern EPA-certified stove at 75% needs about 33% less wood than the same heat load supplied by a 50% open fireplace.
- 1,000 sq ft — about 1.3 cords hardwood in a moderate climate
- 1,500 sq ft — about 1.9 cords
- 2,000 sq ft — about 2.5 cords
- 2,500 sq ft — about 3.2 cords
- 3,000 sq ft — about 3.8 cords
- Severe-climate uplift — roughly ×2 on the moderate figures
Hardwood vs softwood for firewood
Hardwood (oak, maple, hickory, ash, birch) packs roughly 22 million BTU into a cord. Softwood (pine, spruce, fir, cedar) carries about 15 million. The gap is mostly density: hardwood is heavier per cubic foot, so a stacked cord contains more mass to burn.
The premium hardwoods sit higher still. Osage orange tops the chart at 30.7 M BTU per cord. Hickory follows at 27.7 M. White oak and sugar maple cluster around 24 M. Eastern white pine sits at the softwood end at 14.3 M, and spruce drops to 13.5 M.
Softwood often sells for half the price per cord. But you need 50% more of it to deliver the same heat — before counting the extra labour of loading the stove twice as often. For a primary heat source, hardwood usually wins on total cost. Softwood is fine as kindling, shoulder-season fuel, or a top-up for occasional fires.
Why seasoning firewood matters
Freshly cut wood holds 40–50% of its weight in water. Burning it wastes energy boiling that water off before any useful heat reaches the room. Cornell University Cooperative Extension and the University of Maryland Extension both put the usable-heat loss at roughly 40% for green wood compared with properly seasoned wood at 20% moisture or less.
Seasoning time depends on species. Softwoods reach burnable moisture in 6–9 months. Most hardwoods need 12–18 months. Dense species — oak in particular — want 18–24 months. The wood needs airflow, partial sun, and a cover that keeps rain off the top without sealing the sides.
A moisture meter costs around $25 and pays for itself the first season. Wood under 20% on a fresh split face is ready to burn. Wood between 20% and 25% will smoulder and produce creosote — the tar-like deposit that drives most U.S. chimney fires.
Buying and storing firewood
U.S. cord prices in 2024 ran roughly $150–$250 for hardwood and $75–$150 for softwood, depending on region and whether the wood is "seasoned" or "green" at sale. Spring and early summer give the best prices — demand has dropped off and sellers want to move inventory before the next cutting cycle.
Storage is half the battle. A cord stacked on bare ground without cover absorbs moisture from below and rain from above; even hardwood will start to rot within two years. The U.S. Forest Service and most extension services recommend a 4–6 inch gap above the soil (pallets or 2×4s on bricks), a roof or tarp covering only the top of the stack, and full air exposure on the sides.
- Footprint per cord — 4 ft × 8 ft × 4 ft of stack space
- Weight per cord — ~5,000 lb dry hardwood, ~3,500 lb dry softwood
- Drying ground gap — at least 4 inches, ideally pallets
- Cover — top only; never wrap the sides
- Distance from house — 20 ft minimum (termites, carpenter ants)
Common firewood mistakes
"Seasoned" is loosely regulated. Many sellers call wood seasoned after a single summer in the round, before it is split. A split log dries far faster than an intact round — the cut faces are where moisture leaves. Test with a meter before you stack.
An open masonry fireplace runs at 10–20% useful heat output. Most of the warmth disappears up the chimney along with house air the fire pulls in for combustion. If you rely on a fireplace as primary heat, expect roughly double the cord count of the figures in the table above.
Burning unseasoned wood, smouldering fires, and softwood-heavy mixes all accelerate creosote buildup. The National Fire Protection Association attributes around 25,000 U.S. chimney fires per year to creosote deposits. Annual inspection and sweeping are the standard preventive.