FAS vs. #1 Common Lumber: The 80% Rule for Cost Per Clear Board Foot
FAS vs. #1 Common Lumber: The 80% Rule for Cost Per Clear Board Foot - A step into the workshop.
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Two stacks of 4/4 white oak on the same rack. Same species, same thickness, same yard. One tag says FAS. The other says #1 Common, and it's a lot cheaper. Most people standing there decide on gut — pay up for the clean stuff, or grab the cheap pile and plan on eating the waste.
Both of those are guesses, and they don't have to be. Hardwood grades aren't adjectives. They're fractions. The arithmetic that tells you which stack is actually cheaper fits on the back of your cut list.
Grades Are Fractions, Not Adjectives
The National Hardwood Lumber Association's grading rules card doesn't describe FAS as "nice." It defines it: minimum clear yield of surface measure × 10, which is 83⅓%, or 10/12 of the board. No. 1 Common is S.M. × 8 — 66⅔%, 8/12. The American Hardwood Export Council's illustrated guide adds the part people skip, that No. 1 Common runs "from 66⅔% (8/12ths) up to, but not including, the minimum requirement for FAS." So #1C is a band with a floor, not a target.
The size floors differ too. FAS wants a board at least 6" × 8' and clear cuttings of at least 4" × 5' or 3" × 7'. No. 1 Common takes boards down to 3" × 4' and cuttings down to 3" × 3' or 4" × 2'. Hold onto that, because it's where the money is.
One more piece of plumbing. NHLA is explicit that the percentage is figured on surface measure, not board feet: "thus all boards, no matter the thickness, are graded the same." Surface measure is width in inches × length in feet ÷ 12, rounded. Board feet is S.M. × thickness. You get graded on area and billed on volume. Buy 8/4 and you're buying the same proportion of clear wood as 4/4 at twice the board footage, so the dollar cost of the grade's waste allowance doubles with thickness. Nobody mentions that at the register.
The 80% Rule
Cost per guaranteed-clear board foot is price divided by yield. FAS is price ÷ 0.8333. #1 Common is price ÷ 0.6667. Divide the two guarantees into each other and you get 8/10 — exactly 0.80.
No. 1 Common is cheaper per guaranteed-clear board foot whenever it's priced under 80% of FAS. Said the other way: whenever the FAS premium tops 25%.
That's not a rule of thumb somebody published. It's the two NHLA definitions divided by each other, which is why you can trust it and why you can run it in your head at the rack.
Two Real Racks, Two Different Answers
Rustic Lodge Works, a sawmill in Hanceville, Alabama, publishes a March 2026 price list showing white oak 4/4 #1 Common at $4.00 a board foot and white oak 4/4 FAS at $6.18. That's a 54.5% FAS premium, which puts #1C at 64.7% of the FAS price — well under the 80% line.
Run it out. FAS costs $6.18 ÷ 0.8333 = $7.42 per guaranteed-clear board foot. #1C costs $4.00 ÷ 0.6667 = $6.00. The cheap grade is 19.1% cheaper on wood you can actually use. Break-even sits at 53.9% actual yield — below #1 Common's own legal floor, so it can't get there. Best framing of the whole thing: at its worst legal yield, #1 Common at $6.00 still beats FAS at a theoretically perfect 100% yield, which would be $6.18. Worth noting Rustic Lodge's list doesn't say whether that stock is kiln dried or green, rough or surfaced, so price it as a sawmill price and go look at it.
Now the other pair. Advantage Lumber lists 4/4 red oak "#1 Lumber" at $2.70/BF and standard 4/4 red oak at $3.60/BF. Their domestic hardwoods index says "All grades are Select & Better unless noted," which is the only reason I can put a grade on that $3.60 listing — the product page itself prints none, so I'm calling it Select & Better by inference, not FAS. That's a 33.3% premium, #1C at 75% of the upper price. Per guaranteed-clear board foot: $4.32 versus $4.05. #1 Common wins by 6.2%. Break-even yield, 62.5%.
Same math, wildly different margins. The answer tracks the spread on your rack, and a dealer running a 20% premium flips it entirely. I'm not going to hand you a national FAS premium, because the confident "FAS is 40–60% more" numbers floating around trace back to auto-generated price-guide sites and not to any dealer or standards body. Two verified same-dealer pairs is what exists. Bring a calculator.
Where the Cheap Grade Over-Delivers
Here's the mechanism the price tags don't explain. FAS allows you S.M. ÷ 4 cuttings. No. 1 Common allows (S.M. + 1) ÷ 3 — more cuttings, and smaller ones. A board can be genuinely clean and still get knocked down purely on count.
NHLA's own published No. 1 Common example shows how thin the margin can be. A 6" × 14' board, S.M. 7, with two clear cuttings of 6" × 4' (24 cutting units) and 6" × 7' (42 units) totals 66 units. It needs 56 to make #1C, so it passes easy.
At Rustic Lodge's $4.00, that 7-board-foot piece costs $28.00 and carries 5.5 board feet of clear wood. $5.09 per clear board foot, against FAS's $7.42 guaranteed-minimum cost.
Purdue Extension's worked examples show the same thing from the other side, on identical 6" × 8' boards with 48 total units. One yields a single 6" × 7' cutting — 42 units against the 40 required — and makes FAS at 87.5% clear. The other yields a 6" × 5'4" cutting, 32 units against 32 required, and just barely scrapes into No. 1 Common at 66.7% clear.
Then there's the part nobody talks about. The USDA Forest Products Laboratory's Wood Handbook shows #1 Common's requirement isn't flat — it ratchets up hard on small boards. A No. 1 Common board of 1 square foot surface measure must be 100% clear. A 2-square-foot board must be 75%. The narrow, short, awkward #1C boards everybody walks past carry a better guarantee than the grade's headline number.
If you're cutting drawer fronts, box sides, rails, and stiles, two cuttings isn't a limitation. It's the plan. FAS is charging you a premium for a constraint you don't have.
Ask It for Long Parts and It Gets Cooked
This is the honest counterweight, and the article's a lie without it. That 66⅔% only holds down to cuttings of 3" × 3' or 4" × 2'. Demand longer parts out of one cutting and the guarantee quits covering you.
Hiram Hallock's 1980 Forest Products Laboratory paper FPL 370, on cutting yields when gang ripping, put measured numbers on it. For No. 1 Common at a 1.5-inch rip width, the adjusted cumulative yield for cuttings of a given length or longer:
| Cutting length | Yield from No. 1 Common |
|---|---|
| 60" and longer | 36.0% |
| 48" and longer | 46.3% |
| 26" and longer | 61.9% |
| 12" and longer | 69.3% |
That curve is the whole story. Ask #1 Common for five-foot parts and it hands you 36% — barely half what the grade promises. Ask it for one-foot parts and it hands you 69.3%, which is more than the grade promises.
FPL 370 also ranked grades by part length, and its breakpoints landed at 70"+ for FAS and Selects, 40"–70" for No. 1 Common, and 10"–40" for No. 2 Common. Do not shop off that table — the paper explicitly pegs it to October 1979 prices and says the breakpoints "will change with lumber grade price structure." What's durable is the shape, and the fact that the 40" line sits just above #1C's three-foot minimum cutting. The arithmetic and the grade rules agree with each other.
Carry the caveats: FPL 370 models a furniture plant that gang-rips first and edge-glues panels, assumes glued joints are fine everywhere, and reports two-face-clear cuttings. It's the best measured data on this question and it is not your bench. Hallock was blunt about the limits too, writing that "no simple method exists to determine the lowest cost mix of lumber grades that will cut a specific cutting bill" — a true least-cost answer needs linear programming. His practical advice was to split the cutting bill by length and buy a different grade for each pile.
Walnut Is Exactly Where This Falls Apart
Purdue Extension flags a species exception that torches a lot of casual advice, and it lands on the most popular premium hobbyist species there is. The grades for walnut and butternut "vary substantially from the standard grades" — FAS admits 6- and 7-foot pieces instead of 8, minimum FAS width drops to 5 inches from 6, and minimum cutting sizes shrink across all grades. Purdue's conclusion: "any particular grade in walnut and butternut will not yield the size and probably surface area of clear material, as compared to lumber graded with the standard rules."
FAS walnut is a weaker promise than FAS oak. The premium is least defensible exactly where people most often pay it.
The other trap is the label. Per NHLA and AHEC, FAS means FAS on both faces. F1F and Selects mean an FAS face and a No. 1 Common back — Selects just allow smaller boards, 4" × 6' against F1F's 6" × 8'. So "Sel & Btr" is often near-FAS money for a board whose back face is the cheap grade. On a drawer front, that back face is glued to something.
And you may not get the choice. Ocooch Hardwoods sells walnut and cherry as Select & Better only, no lower grade offered, at $9.55/bdft for 4/4 walnut S2S and $5.25/BF for 13/16" cherry. Capturing this saving often means a sawmill or a rough-lumber yard, not a mail-order shop. While you're there, watch the width upcharges — Rustic Lodge adds 20% at 10" and wider, Johnson Creek Hardwoods adds 20% at 10" and 50% at 14". The wide boards that carry the grade premium frequently carry a second premium stacked on top.
What I'd Actually Do
Sort your cut list by length first, then price the rack. If your longest part is under three feet, buy #1 Common wherever it's under 80% of the upper grade and stop agonizing. If you need six-foot rails out of one clean cutting, pay for FAS and don't pretend the arithmetic says otherwise.
Two things not to double-count against the cheap grade: NHLA's standard surfacing already takes 4/4 rough from 25.4mm down to 20.6mm S2S, in both grades. And Ocooch tells buyers to expect 10–20% waste on S2S stock, which is also both grades. That's the cost of lumber, not the cost of #1 Common.
Right tool for the job goes for material too. FAS is a tool for long clear parts. For everything else, you're buying a percentage you'll never cut.