Firewood Cord Calculator (+ BTU by Species)
Measure your woodpile — length, height, and depth — and this calculator converts it to cords and face cords, then goes a step further than most: pick the species and it estimates the actual heat (BTU) in the stack, what that’s worth next to heating oil, and — if you enter the price — what you’re really paying per million BTU. Two “cords” of different species are not the same amount of heat, and this is the tool that shows the difference.
What counts as a cord (and what doesn’t)
A full cord is a legal unit in most states: a stack 4 ft high × 4 ft deep × 8 ft long = 128 stacked cubic feet, air spaces included. A face cord (or “rick”) is the same 4 × 8 ft face but only one log-length deep — so its actual volume depends entirely on how long the logs are. At 16-inch logs, a face cord is exactly one third of a full cord; sellers quoting “a cord” of 16-inch wood stacked one row deep are offering a third of what the word means.
The formulas (so you can check the math)
Stacked volume (cu ft) = Length ft × Height ft × (Log length in ÷ 12)
Cords = Volume ÷ 128
Face cords = Cords × (48 ÷ log length in inches)
Heat in the stack = Cords × species BTU rating (ratings are for seasoned wood at ~20% moisture — green wood wastes a third of its energy boiling off water)
Delivered heat = Heat × stove efficiency (modern EPA stoves run ~70–77%; open fireplaces as low as 10%)
Heating-oil equivalent = Delivered BTU ÷ (138,500 BTU/gal × 85% boiler efficiency)
Species ratings are approximate averages from published firewood BTU charts; charts disagree by a million BTU here and there, but the ranking — hickory and oak at the top, pine and aspen at the bottom — is universal.
Worked example
A pickup-load stacked 12 ft long × 4 ft high, 16-inch logs, red oak, burned in a modern stove:
Volume = 12 × 4 × 1.33 = 64 cu ft → 64 ÷ 128 = 0.5 cord (= 1.5 face cords)
Heat = 0.5 × 24.6 = 12.3 million BTU → × 70% = 8.6 million BTU into the room
That’s the heat of roughly 73 gallons of heating oil. If you paid $200 for the load, you’re at $23 per million BTU delivered — now you have a number to compare against the next seller’s “cord,” and against your oil bill.
Who this is for
Anyone buying firewood by the cord, face cord, rick, or “truckload” — the vocabulary is where buyers get taken, and stacking math is the defense. It pairs naturally with the rest of the fire chain on this site: cutting your own wood starts with a homeowner chainsaw (or a small gas saw for limbing and bucking), and burning it well ends with a proper log burner — the stove-efficiency input above is exactly why stove choice changes the value of every cord you buy. Measuring logs you haven’t split yet? Volume of round wood is a different problem — the wood CFT calculator handles solid-volume math.
Frequently Asked Questions
How much firewood is in a face cord?
Depends on the log length — that’s the trick of the term. A face cord is a 4 × 8 ft face one log deep: at 16-inch logs it’s 1/3 of a full cord, at 12-inch logs 1/4. Convert face-cord prices to full-cord prices before comparing sellers (the calculator does it for you).
Does the species really matter that much?
Nearly 2× between the extremes. A cord of hickory (~27.7 M BTU) carries almost twice the heat of a cord of aspen (~14.7). At equal prices per cord, dense hardwood is by far the better buy — the only reasons to burn softwood are kindling, shoulder-season fires, and free wood.
Is a “truckload” of firewood a cord?
Almost never. A full-size pickup bed holds about half a cord loosely thrown, a third stacked tight. If a seller claims a full cord fits in one pickup trip, measure the stack when it lands — 4 × 4 × 8 ft is easy to verify.
Do the BTU numbers work for green (unseasoned) wood?
No — ratings assume ~20% moisture. Fresh-cut wood is 50%+ water, and a big share of its energy goes to boiling that off (while creosoting your chimney). Season splits 6–12 months under cover; hardwoods like oak want the full year.