Reference Guide
Hardwood Lumber Buying Guide
Buying hardwood is a different transaction from buying construction lumber. You are paying by volume, choosing a surfacing level, and adding waste you will not see until the board is on the bench. Understand the quarter system and the board foot, and you can walk into the lumber yard with a number instead of a guess.
Rough sawn vs. S2S vs. S4S
The three surfacing levels tell you how much milling is left for you — and how much of the board you are actually buying.
| Level | Means | Who it suits |
|---|---|---|
| Rough sawn | No surfacing; planer marks and rough faces | Shops with a jointer & planer wanting the lowest price per BF |
| S2S | Surfaced two sides; both edges still rough | Most furniture builds; edges squared after gluing or ripping |
| S4S | Surfaced four sides; faces and edges cleaned up | Ready-to-finish trim and small parts with no further milling |
Rule of thumb: the more surfaces the mill touches, the less thickness and width you get, but the less wear and tear on your own machines.
The quarter system
Hardwood thickness is quoted in quarters of an inch — the nominal rough thickness before surfacing. A "4/4" board started life at 1" thick; after planing it usually finishes around 13/16". You pay on the rough quarter, then lose a little to the planer.
| Quarter | Rough thickness | Typical finished (S2S) | Common use |
|---|---|---|---|
| 4/4 | 1" | 13/16" (3/4") | Cabinet doors, drawer sides, panels |
| 5/4 | 1-1/4" | 1-1/16" (1") | Table aprons, stair treads, counter edges |
| 6/4 | 1-1/2" | 1-5/16" (1-1/4") | Legs, thick rails, turning blanks |
| 8/4 | 2" | 1-13/16" (1-3/4") | Table legs, thick posts, resawing |
| 12/4 | 3" | 2-13/16" (2-3/4") | Heavy timbers, thick legs, big turnings |
Finished thickness varies with the mill and how hard your planer has to work. Always measure the board you are holding — not the nominal quarter.
The board-foot formula
A board foot (BF) is 144 cubic inches — a board 1" thick, 12" wide, and 12" long. To find the board feet in a piece, multiply thickness × width × length in inches and divide by 144. If you measure length in feet, divide by 12 instead.
Board feet = (Thicknessin × Widthin × Lengthin) ÷ 144
Or, with length in feet: (T × W × Lft) ÷ 12
Worked example: a 1" thick (4/4), 6" wide, 8-foot board is(1 × 6 × 8) ÷ 12 = 4 board feet. At $7/BF, that board costs $28. The board foot & lumber cost calculator does this for a whole cut list and totals the price.
Waste factors: buy more than the net
A cut list gives you net dimensions. Real boards give you defects, checks, sapwood, and snipe. Add a waste factor before you order:
| Stock | Waste allowance | Why |
|---|---|---|
| Straight-grained hardwoods | 15% | Clean FAS stock with predictable yields |
| Rustic / knotty stock | 20%–25% | More defects to cut around and cull |
Add the percentage to your net board feet and round up to the next whole board. It is cheaper to have a spare board than to make a second trip across town mid-project.
At the lumber yard
- Bring a moisture meter — air-dried stock should read in the 6–8% range for interior work.
- Inspect both faces and edges for checks, pith, and wane before it goes on the cart, not after it is on the rack.
- Buy 10–15% over your net even on clean stock, and more for figured or rustic boards.
- Let lumber acclimate to the shop for several days before milling so it moves before it is final thickness.