Bottom Line Up Front (BLUF): How to Calculate Board Feet
One Board Foot (BF or FBM) represents a volume of 144 cubic inches. Formula: Board Feet = (Thickness in Inches × Width in Inches × Length in Feet) / 12. If length is in inches: Board Feet = (Thickness × Width × Length) / 144. Multiply total BF by price per board foot for cost.
Mastering Hardwood Volume, Quarters & Lumber Buying
1. The Board Foot Volume Unit Explained
Unlike dimensional softwood lumber (like 2x4s sold by linear foot), rough-sawn hardwood is sold by volume in Board Feet (BF). 1 BF equals a 1-inch thick board that is 12 inches wide and 12 inches long (144 in³ or 0.00236 m³).
2. Understanding Hardwood Quarters (4/4, 5/4, 8/4)
Sawmills express rough hardwood thickness in quarter-inch increments: 4/4 ("four-quarter") = 1.0" rough (plans down to 3/4" or 13/16"), 5/4 = 1.25" rough (plans to 1.0"), 6/4 = 1.5" rough (plans to 1-1/4"), and 8/4 = 2.0" rough (plans to 1-3/4").
3. Accounting for Milling Scrap & Defects
Rough hardwood boards have knots, sapwood, checking, and bow/cup. Always purchase a 15% to 20% waste allowance (25% for complex curved furniture parts) to ensure enough usable yield after jointing and planing.
Hardwood Quarters to Planed Thickness Reference Chart
| Hardwood Quarter | Rough Sawmill Thickness | Surfaced/Planed (S2S) Thickness | Common Applications |
|---|---|---|---|
| 4/4 ("Four-Quarter") | 1.00 inch (25.4 mm) | 0.75" to 0.81" (3/4"–13/16") | Cabinet doors, drawer sides, face frames |
| 5/4 ("Five-Quarter") | 1.25 inches (31.8 mm) | 1.00" to 1.06" (1"–1-1/16") | Heavy table tops, desk surfaces, stair treads |
| 6/4 ("Six-Quarter") | 1.50 inches (38.1 mm) | 1.25" to 1.31" (1-1/4") | Stout furniture frames, chairs, architectural trim |
| 8/4 ("Eight-Quarter") | 2.00 inches (50.8 mm) | 1.75" (1-3/4") | Dining table legs, butcher blocks, workbench tops |
| 12/4 ("Twelve-Quarter") | 3.00 inches (76.2 mm) | 2.75" (2-3/4") | Turnings, heavy bed posts, structural timber |
Frequently Asked Questions about Board Feet & Hardwood
What is the difference between linear feet, square feet, and board feet?
Linear feet measures only length (1D). Square feet measures surface area (2D: length × width). Board feet measures 3D volume (length × width × thickness / 12).
How do you calculate board feet if thickness is less than 1 inch?
In commercial lumber yards, any board thinner than 1 inch (such as 1/2" or 3/4" stock) is typically billed at the full 1-inch (4/4) rate for board foot calculations unless specially surfaced.
Why do hardwood lumber dealers use quarters?
Quarters describe rough un-surfaced board thickness directly from the sawmill blade before shrinkage and surfacing loss occur during kiln drying.