Calculator
Firewood Cord Calculator
A cord is a fixed volume — 4 by 4 by 8 ft, 128 cubic feet, no argument about it. A face cord is not a fixed volume at all: it's 4 by 8 ft by however long the logs happen to be, and that third dimension is exactly the part most firewood disputes turn on. A face cord of 12 in logs and a face cord of 24 in logs are stacked to the same face, look identical from the front, and hold twice as much wood in one case as the other.
This calculator works from your stack's actual dimensions rather than assuming a standard log length, and reports both the full-cord and face-cord figures together with how many face cords of your specific log length make one real cord. That relationship — not a flat conversion — is the number worth knowing before agreeing on a price quoted in face cords rather than full cords.
Calculate your quantity
This is the stack depth, and it is what a face cord leaves undefined.
million BTU
Full cords
0.667 cords
Face cords
2 face cords
- Stacked volume
- 85.3 cu ft
- Stack depth
- 1.333 ft
- Face cords in one full cord
- 3 face cords
- Weight, seasoned
- 2,800 lb
- Heat content
- 16 million BTU
- Heating oil equivalent
- 116 gallons
- Winters covered
- 0.27 winters
- At 16 in logs it takes 3 face cords to make one full cord. A seller quoting "a cord" at 16 in depth for a face-cord price is quoting 33% of a cord.
Shopping summary
- • 0.67 full cord(s) of oak, hickory, beech
This is an estimate — confirm structural work with a professional.
How this calculation works
Stack volume is straightforward once log length is converted to feet: length times height times depth, where depth is just the log length in inches divided by 12. A full cord is that volume divided by 128, the fixed cubic footage a cord has always meant regardless of how the wood inside it is cut. A face cord is defined differently — it's always 4 ft high by 8 ft long, but its depth is whatever the logs are, so face-cord volume itself changes with log length even though the visible face doesn't.
Dividing 128 by that face-cord volume gives the number of face cords in one true cord, and it's this figure — not the stack size — that actually varies job to job. At 16 in logs, a common stove length, three face cords make one full cord almost exactly, because 4 x 8 x (16/12) works out to 42.67 cubic feet and 128 divided by that is 3. Cut the same wood to 12 in fireplace lengths instead and it takes four face cords to make a cord; cut it to 24 in and it only takes two.
- Species changes weight and heat content, not volume — a cord of oak and a cord of pine occupy the same 128 cubic feet but the oak weighs and burns roughly 60% more.
- The oil-equivalent figure converts heat output into the gallons of heating oil that would deliver the same energy, useful for comparing a wood-heating plan against an existing oil or propane system.
- Winters covered assumes a fixed seasonal heat demand you enter — it's a rough planning figure, not an account of how a particular stove or fireplace actually performs.
- A tightly stacked pile and a loosely thrown one of the same outer dimensions do not hold the same amount of solid wood; this calculator assumes a reasonably tight stack, the way cordwood is conventionally measured.
The formula
fullCords = (stackLength x stackHeight x logLength/12) ÷ 128; faceCordsPerFullCord = 128 ÷ (4 x 8 x logLength/12)
- stackLength x stackHeight
- The face of the stack as you'd see it standing in front of it, in feet — the two dimensions that stay fixed regardless of how long the individual logs are cut.
- logLength / 12
- Log length converted from inches to feet, which becomes the stack's depth — the dimension a face cord leaves undefined until you specify it, and the one that actually decides how much wood a 'cord' quoted informally contains.
- 128
- Cubic feet in one true cord — a fixed measure (4 x 4 x 8 ft) regardless of how the wood inside it is cut. This is the number a face cord is always being compared against.
- faceCordVolume
- 4 x 8 x logLength/12 — a face cord's actual cubic footage, which changes with log length even though its 4 by 8 ft face never does. Two face cords of different log lengths are visually identical and volumetrically different.
- faceCordsPerFullCord
- 128 divided by faceCordVolume — how many face cords, at this specific log length, add up to one true cord. This is the figure that turns a face-cord price into a comparable per-cord price.
Full cords and face cords answer different questions and this page deliberately reports both rather than picking one: a full cord tells you the actual volume of wood, while a face cord tells you what will physically fit against a wall in a single stacked row — both are legitimate ways to think about a firewood order, and the confusion is only in treating a face-cord quote as though it were a cord-sized one.
Where these numbers come from
- 128 cu ft (4 x 4 x 8 ft) as one cord
- A standardized measure of stacked firewood used across the US firewood trade and written into weights-and-measures law in most states — this is the one figure on this page that isn't a convention or an estimate, it's a fixed definition.
- Heat content by species group: roughly 24, 20 and 15 million BTU per cord
- Commonly published seasoned-firewood BTU tables (grouped by hardwood density, from oak/hickory down to softwoods like pine and spruce), widely cited by extension services and firewood suppliers. Actual heat output varies with moisture content, so an unseasoned or poorly dried cord will underperform these figures noticeably.
- Seasoned weight by species group: roughly 2,600 to 4,200 lb per cord
- Commonly published seasoned-firewood weight tables, again grouped by species density. These figures assume properly seasoned wood at roughly 20% moisture content — green, unseasoned wood can weigh meaningfully more per cord.
- 138,500 BTU per gallon of heating oil
- A commonly cited energy-content figure for No. 2 heating oil, used here only to convert a cord's heat output into a directly comparable fuel-oil gallon figure — useful for sizing a wood-heat plan against an existing oil system's seasonal usage.
Worked examples
A rick of oak cut to 16 in stove lengths
| Stack length | 16 ft |
|---|---|
| Stack height | 4 ft |
| Log length | 16 in |
| Species group | Oak, hickory, beech |
| Heat used per winter | 60 |
| Full cords | 0.667 cords |
|---|---|
| Face cords | 2 face cords |
| Stacked volume | 85.3 cu ft |
| Stack depth | 1.333 ft |
| Face cords in one full cord | 3 face cords |
| Weight, seasoned | 2800 lb |
| Heat content | 16 million BTU |
| Heating oil equivalent | 116 gallons |
| Winters covered | 0.27 winters |
This stack is exactly 2 face cords by the way it's built — 16 ft long against an 8 ft face-cord length — and at 16 in logs, this page's arithmetic confirms the number firewood buyers hear most often: three face cords make one true cord. Two face cords here is therefore two-thirds of a cord, 0.667 on the nose, which is what the full-cords figure shows directly.
At oak's roughly 24 million BTU per cord, two-thirds of a cord holds about 16 million BTU — the equivalent of around 116 gallons of heating oil, and enough to cover about a quarter of the 60 million BTU seasonal demand entered here. If a seller quotes this exact stack as 'a cord' rather than two face cords, they're offering a third of what the word actually means.
A larger stack of maple cut to 20 in fireplace lengths
| Stack length | 24 ft |
|---|---|
| Stack height | 4 ft |
| Log length | 20 in |
| Species group | Maple, birch, ash |
| Heat used per winter | 80 |
| Full cords | 1.25 cords |
|---|---|
| Face cords | 3 face cords |
| Stacked volume | 160 cu ft |
| Stack depth | 1.667 ft |
| Face cords in one full cord | 2.4 face cords |
| Weight, seasoned | 4500 lb |
| Heat content | 25 million BTU |
| Heating oil equivalent | 181 gallons |
| Winters covered | 0.31 winters |
This stack is bigger and holds more wood — 1.25 full cords against the first example's 0.667 — but notice the ratio changed along with the log length: at 20 in, it now takes only 2.4 face cords to make a true cord, not three. The same face-cord count (3, in this case) represents more actual wood at 20 in logs than it would at 16 in, purely because the depth term grew.
That's the arithmetic worth carrying into any firewood negotiation priced by the face cord: ask the log length before agreeing to a per-face-cord rate, because the same stated quantity can mean anywhere from a third to a half of a true cord depending on it. At maple's 20 million BTU per cord, this order holds 25 million BTU — a bigger share of an 80 million BTU winter than the first example covered of its own, smaller seasonal target.
Common mistakes
- Treating a face cord as roughly a third of a true cord in every case. That ratio only holds at 16 in logs specifically — at 12 in it's a quarter, at 24 in it's a half, and the difference between those is real money on a full-season order.
- Comparing prices quoted in face cords from two sellers without confirming both are cutting to the same log length. A cheaper price per face cord at a longer log length can easily be the worse deal per actual cubic foot of wood.
- Assuming green, freshly cut wood delivers the same heat output as the seasoned-wood BTU figures this page uses. Unseasoned wood can lose a meaningful share of its usable heat to driving off moisture rather than warming a room, and burns dirtier while doing it.
- Stacking loosely and expecting a full cord's worth of wood in a full cord's worth of outer dimensions. Gaps between rounds and unevenly split pieces reduce the actual solid-wood volume below what a tightly stacked cord assumes.
- Using a single species' BTU figure for a mixed load. A truckload described as 'mixed hardwood' spans the softwood-to-hardwood range this page's three species groups cover, and the honest heat-content estimate is somewhere between them, not at either end.
Shopping summary
Order in full cords whenever a seller will quote that way — it removes the log-length ambiguity entirely. Where face cords are the only unit on offer, get the log length in writing along with the price, since that's the number this page needs to tell you what you're actually being quoted per true cord.
If the wood is heating a space rather than a fireplace used occasionally, the BTU calculator sizes the heating load itself, and comparing that figure against this page's seasonal winters-covered output is a useful sanity check before committing to a full season's supply in one delivery.
FAQ
Why do firewood sellers use face cords at all if they're this ambiguous?
Because a face cord is easy to see and stack to — 4 by 8 ft is a simple row against a wall, and it's a natural unit for delivery and stacking regardless of log length. The ambiguity isn't in the stacking, it's in treating the word 'cord' loosely when what's actually being sold is a face cord at an unstated depth.
Does a full cord weigh the same regardless of species?
No — density varies enough between species groups that a cord of a dense hardwood like oak can weigh 60% more than the same 128 cubic feet of a softwood like pine, even though both fill the same physical space. Weight, heat output and volume are three different figures this page tracks separately for exactly that reason.
How accurate is the winters-covered figure?
It's a rough planning ratio — total heat content divided by a seasonal demand figure you enter — not an account of stove efficiency, insulation, or how cold a specific winter runs. Use it to compare orders against each other or against a rough personal usage estimate, not as a guarantee of exactly how far an order will stretch.
Is kiln-dried or extremely well-seasoned wood worth more heat than these BTU figures suggest?
It can burn closer to its theoretical maximum heat content than wood at typical 20% seasoned moisture, since less energy is spent driving off water during combustion. The BTU figures here already assume reasonably well-seasoned wood, so kiln-dried wood is a modest upgrade on these numbers, not a dramatically different one.
What log length should I ask a seller to cut to if I have a choice?
Whatever fits your stove or fireplace with an inch or two of clearance on each end — shorter logs split more easily and season faster, but a shorter log length also means more face cords are needed to make up a true cord, which is worth knowing when comparing a per-face-cord price across two different cut lengths.
Does stacking height matter beyond the standard 4 ft face cord height?
This calculator uses your entered stack height directly rather than assuming 4 ft, so a taller or shorter stack (a rick built along a shed wall, for instance) is handled correctly as long as the height and length you enter match what's actually stacked — only the face-cord comparison figure assumes the conventional 4 ft height, since that's the definition a face cord is built on.
Where to go next
The projects this number is a step of, the guides that explain the method behind it, and the rest of its trade group.