How to calculate cubic feet for wood
Wood volume calculations show up in two main places: stacked firewood (sold by the cord) and lumber (sold by the board foot). Both reduce to cubic feet — multiply length × width × depth in feet for the raw stack volume.
For loose-stacked firewood, only ~80% of the gross stack is solid wood. Tight, uniform splits get closer to 90%.
Worked examples
Example 1: A 16 ft × 4 ft × 4 ft firewood stack
16 × 4 × 4 = 256 ft³ = 2 full cords.
Example 2: 50 ft³ of rough oak lumber
50 × 12 = 600 board feet; weight ≈ 50 × 47 = 2,350 lbs air-dried.
Example 3: A face cord (4 ft × 8 ft × 16 inches)
4 × 8 × 1.333 = 42.67 ft³ = 1/3 cord.
Wood density (air-dried)
| Species | Conversion factor | Worked example |
|---|---|---|
| White oak | ~47 lb/ft³ | 1 cord ≈ 6,016 lbs |
| Sugar maple | ~44 lb/ft³ | 1 cord ≈ 5,632 lbs |
| Hickory | ~50 lb/ft³ | 1 cord ≈ 6,400 lbs |
| Birch | ~40 lb/ft³ | 1 cord ≈ 5,120 lbs |
| Pine (white) | ~25 lb/ft³ | 1 cord ≈ 3,200 lbs |
| Cedar | ~22 lb/ft³ | 1 cord ≈ 2,816 lbs |
| Walnut | ~38 lb/ft³ | 1 ft³ ≈ 38 lbs |
Tips and considerations
Confirm cord size before paying
"Truck loads," "ricks," and "face cords" are not standardized. Insist on a 4×4×8 ft stack measurement (or proportionally equivalent), not a vague "truckload."
Season wood at least 6 months
Freshly split firewood holds 30–50% moisture. Burn at 20% or less for clean efficient heat — that means stacking in a sunny, ventilated spot for at least a full summer.
Common mistakes to avoid
- Using nominal lumber dimensions. A “2×4” is actually 1.5 × 3.5 inches. For volume math, use real measurements.
- Confusing board feet with cubic feet. 1 board foot = 1/12 cubic foot. A 100 board-foot order is only about 8.3 cubic feet of usable wood.
- Mixing cords and face cords for firewood. A full cord is 128 ft³ (4 × 4 × 8 ft stacked). A face cord is one-third of that. Confirm which one your supplier means.
- Forgetting wood density varies by species. Pine is about 30 lb/ft³ dry; oak is 47 lb/ft³. Trailer load limits depend on which one you ordered.
Related concepts and calculators
Lumber and firewood math uses several adjacent units:
- Cubic feet to board feet — the standard hardwood-lumber unit.
- Linear feet to cubic feet — going from board length to volume given a known cross-section.
- Cubic feet to pounds — wood weight varies dramatically by species.
- Subwoofer enclosure — board cuts and internal volume share the same math.