Rough-Sawn vs. S4S Lumber: Real Cost per Usable Board Foot

Yo, let me tell you about the sticker shock that started this whole thing. I'm staring at Advantage Lumber's listing for an S4S 1x10 white oak board at $23. One board. And across town, a mill is selling rough white oak by the board foot like it's nothing. Rough is "often 30 to 50% cheaper per board foot than S4S," straight from Advantage Lumber's comparison. So obviously rough wins, right?

Slow down. Because board-foot price is not cost per board foot you can actually use. And nobody at the mill is going to volunteer the math.

You Paid for an Inch, You Got Thirteen-Sixteenths

Here's the mechanic that changes everything. Rough 4/4 hardwood comes off the saw at a full inch. S4S 4/4 comes to you at 13/16" or 3/4". Where did the rest go? Face jointing takes 1/16" to 1/8" per side to flatten the board, planing takes another 1/32" to 1/16" per face to smooth it — Craftsmen Supply Center puts the total loss at 1/8" to 1/4" from rough to finished. CalcCorp runs it more aggressively, saying that once you straight-line both edges too, S4S loses roughly 5/16" total and 4/4 lands nearer 11/16" to 3/4".

Either way, here's the part that stings: the board-foot price is billed on the nominal rough thickness regardless of what you walk out with. CalcCorp does the division — billed at 1", delivered at 13/16", which means you paid about 23% more thickness than you took home. Surfacing is a service, not a discount. And the surfacing fee itself is small potatoes anyway, typically $0.10 to $0.20 per board foot at a dealer. The real charge is hidden in the thickness.

So when you buy rough, you're not just saving the sticker difference. You're keeping the wood that S4S buyers pay for and throw away. That's the actual arbitrage.

The Price Table, and the Big-Box Markup

CalcCorp's 2026 4/4 FAS rough, kiln-dried ranges: poplar $3.50–$6.50, red oak $4.50–$8.00, cherry $6.00–$9.00, hard maple $7.00–$10.00, white oak $7.00–$11.00, walnut $10.00–$18.00 per board foot. CustomWoodQuote's early 2026 table runs similar: walnut $6–$12 rough versus $10–$18 surfaced, white oak $5–$10 versus $8–$15. Treat all of this as indicative, because both of those are pricing-guide sites, and CalcCorp itself will tell you local markets swing 20–30% either way.

The comparison that made me put my coffee down: CalcCorp figures a 1×4×6-foot S4S red oak board at Home Depot at $15.13. Sounds fine until you compute its actual dimensions — 0.75" × 3.5" × 72" is only 1.3125 actual board feet. That's $11.53 per actual board foot. Against $4.50 rough red oak at a Midwest yard, big-box S4S is a 2.6× premium. Two-point-six. The subway ride home from the mill is free.

The Waste Nobody Puts on the Invoice

Now the ugly column of the spreadsheet. Rough lumber isn't 100% usable. You lose wood to straightening crooked edges, cutting around checks, and matching grain.

How much? Depends who you ask, and honest writers say so. Craftsmen Supply Center says budget 15–20% waste on FAS. CustomWoodQuote says 15–25% for rough-sawn, 25%-plus for wide or figured stock. CalcCorp says 20–30% — 20% for straight rips out of FAS, 30% when you're grain-matching or working No. 1 Common. ToolGrit's calculator says 20% is a safe starting point for clear grades and warns against slapping a flat percentage across all grades. So call it 15–30% and feel out your own species. The sensitivity matters: on a 30-board-foot buy, the difference between 15% and 30% waste is four and a half board feet. Ask me how I know what a "come up three boards short" day looks like. Actually don't.

Grade is the lever here, briefly: FAS has to yield 83-1/3% to 100% clear wood in cuttings of at least 3"×7' or 4"×5', per the NHLA rules Architectural Woods summarizes. FAS runs 40–80% more than No. 1 Common, but Common boards are shorter and narrower, so you buy 10–15% more volume to net the same parts — CalcCorp's math still nets you about 25% savings going Common. Worth it for painted or small parts. Not worth it when you need one continuous clear top.

The Drying Trap at Mill-Direct Prices

This is where the "bargain" green lumber from the local mill gets you. Interior furniture wants 6–8% moisture content — that's the Bessemeter target, and cabinetry folks want 6–7%. Air-drying outdoors bottoms out around 12% outside of desert climates. So that stack of "air-dried, dirt cheap" rough oak? It needs months of stickering in your apartment before it's furniture wood. And in my shop — second bedroom, landlord thinks it's a guest room — "months of indoor stickering" is a marriage counseling issue, not a woodworking step.

The Wood Database's rule of thumb for air-drying is one year per inch of thickness. From green. Run your drying clock long and that "cheap" lumber quietly gains a second lumber's worth of cost.

And drying degrade is real. End grain lets moisture escape 10–12× faster than the faces — seal your ends within minutes of sawing, with AnchorSeal, glue, even latex paint. Case-hardened stock can honeycomb internally, and The Wood Database points out honeycombing is undetectable from the face. You find it on the jointer. After you paid.

Your Time Is a Line Item (I Just Can't Give You the Number)

Here's where I have to be straight with you. Nobody publishes a credible hours-per-100-board-feet figure for milling rough lumber, and I'm not going to invent one. What I can tell you: rough stock needs jointing, planing, and straight-lining, it makes more dust, and it demands real shop time — Advantage Lumber's own comparison says rough requires the tools, the skill, and "significant milling," while S4S needs "minimal" time.

My honest experience milling rough stock in a small shop without dust collection: it's an evening, sometimes two, and my neighbors know about it. Not a number. A vibe. But a real one.

CalcCorp's decision rule is the cleanest I've seen: if you own a planer, buy rough — you keep the material and the thickness choice. If you don't, S2S at $0.20 a board foot is far cheaper than buying a planer for one project. No shame in that. The pros hybridize too, per Advantage Lumber: rough for the big cheap surfaces, S4S for small precise parts. Even S4S still needs final trimming and sanding, so you're never buying your way to zero work.

Running the Actual Math

Take CalcCorp's walnut dining table model, because it's the honest version. Top, aprons, and 8/4 legs come to about 23 net board feet of 4/4 plus 3.2 of 8/4. At 30% waste that's 30 board feet at $10.75 plus 5 at $12.50 — $385, plus $7 in S2S surfacing, $392 total. Skip the waste allowance and you budget $288–$294 and come up short. That's the whole article in one number: the waste factor isn't a footnote, it's a hundred bucks.

So when does mill-direct rough win? When you own a jointer and planer, when you buy kiln-dried or you've genuinely got the space and patience to sticker indoors, and when you budget 20–30% waste up front instead of pretending. When does it lose? Green lumber with no drying plan, no planer, or a project on a deadline. Run the math before the mill runs it on you.

One last lever before you go: the cutoff bin. Shorts and cutoffs are the cheapest hardwood in any yard, already paid for by someone else's optimism. Drawer fronts, boxes, cutting boards. Check it first. Ask me how I got half my Brooklyn shop.