Lumber Grades Explained: FAS, Common, Selects, and What a Grade Actually Buys You

There is not one lumber grading system. There are two, they measure completely different things, and woodworkers conflate them constantly at real cost. Hardwood grades tell you how much clear, defect-free wood you can cut out of a board and say nothing at all about strength. Softwood grades split again, into one ladder for how pretty a face is and another for how much load a piece carries. A "No. 1" oak board and a "No. 1" pine 2x8 have nothing to do with each other. This guide separates the two, gives you the arithmetic the grade names are built on, and then does something I have not seen another guide do: it puts a number on what you actually give up when you drop a softwood grade.

Two Systems, Not One

Start here, because the rest only makes sense once this is straight. The two systems grew up around two different jobs.

Hardwood is bought by furniture and cabinet shops who cut a board up into smaller parts. So the National Hardwood Lumber Association grades hardwood for yield: how much clear, usable wood you can extract as rectangular pieces. A higher grade guarantees more clear area, in fewer and larger pieces. It is an appearance-and-usable-area system, and it is deliberately silent about strength. There is no such thing as a structural hardwood grade in the NHLA rules.

Softwood is bought for two very different reasons, so it has two ladders. One is an appearance ladder for trim, shelving and finish boards, graded on how clean the face looks. The other is a structural ladder for the dimensional 2x material you frame with, graded on how much load it carries, which ties each grade to published engineering design values. Same species, two unrelated ratings. Neither ladder tells you what the wood itself will do, which is a third question again: our guide to domestic hardwoods covers the hardness, stiffness and shrinkage numbers by species.

Hardwood Grades (NHLA): Buying by the Clear Cutting

Nearly all hardwood sold in the US and Canada is graded to one rulebook, the NHLA Rules for the Measurement and Inspection of Hardwood and Cypress. The current edition took effect on 1 January 2023. Two principles drive the whole thing, and once you have them the grade names stop being arbitrary.

First, hardwood is graded from the poorer face. The grader flips the board and grades the worse of the two sides. So the grade is a floor, not an average, and your good face is usually better than the grade implies. There are two exceptions, FAS/1F and Selects, and both work by grading the better face instead.

Second, hardwood is graded by clear "cuttings," not by the whole board. NHLA does not care whether the entire board is clear. It cares how much clear, defect-free wood you can extract as rectangular pieces, because that is what a furniture or cabinet shop actually does with a board. A higher grade demands a higher percentage of clear yield and insists it come in fewer, larger pieces.

The arithmetic the grade names are built on

Here is the machinery most guides skip. Every board has a surface measure, its face area in square feet, rounded to the nearest whole foot. The board is then treated as 12 "units" per square foot, so the total possible units equal surface measure times 12. A cutting's units equal its clear width in inches times its clear length in feet. The grade is whatever fraction of those units you can recover as clear cuttings that meet a minimum size.

That single relationship generates every yield percentage in the grade table. FAS is SM × 10 out of a possible SM × 12, which is 83-1/3 percent. No. 1 Common is SM × 8, or 66-2/3 percent. No. 2 is SM × 6, or 50 percent. The percentages are not round numbers chosen by committee. They are twelfths.

How many cuttings you are allowed

Yield is only half the rule. Each grade also caps how many separate clear pieces you may take to reach that yield, and the cap scales with the size of the board. This is the part that actually decides which grade suits your project, and it is almost never published in plain language, so here it is.

Work an example and the practical meaning falls out. A 10 surface-measure board graded FAS gets 10 / 4 = 2 cuttings (integer division, so two), and those two pieces together must cover 83-1/3 percent of the board. The same board graded No. 1 Common gets (10 + 1) / 3 = 3 cuttings covering 66-2/3 percent. So FAS is not simply "more clear wood." It is more clear wood arriving in bigger continuous pieces. That distinction is the whole basis of the buying advice further down.

The grades, exact specifications

FAS stands for First And Seconds, a survival from the era when the top two grades were sold together. Both faces meet FAS, the board is at least 6 inches wide and 8 feet long, and 83-1/3 percent or more of it is clear. Buy it when you need long, wide, fully exposed clear stock: a one-board tabletop, long clear aprons, a wide rail that shows on every side.

FAS/1F, said "FAS one face" and written F1F, is the split-decision grade. The better face must meet full FAS; the poorer face only has to reach No. 1 Common. Same board size as FAS. You are guaranteed one FAS-quality face, so it is the right buy anywhere only one side shows, and it costs less than FAS because the back is allowed a grade worse.

Selects is F1F's small-board cousin, common in the northern US. Same face rule, but it allows smaller stock, down to 4 inches wide by 6 feet long. Good value for smaller furniture parts where you still want one clean face.

No. 1 Common, often called the cabinet grade, is the workhorse. Boards down to 3 inches by 4 feet, 66-2/3 percent clear, and clear cuttings down to 3" by 3' or 4" by 2'. That minimum cutting size is the whole point: it is the size of most furniture and cabinet parts. Stiles, rails, drawer sides, face-frame stock. For most furniture, No. 1 Common is the smart buy and FAS is a waste of money. If you are cutting a board into pieces shorter than 4 feet, paying FAS money buys you continuity you are about to crosscut away.

No. 2A and No. 2B both allow 50 percent clear yield. The difference is not the amount, it is the kind of cutting: 2A requires clear-face cuttings, 2B allows sound cuttings. So a 2B board can carry a sound tight knot or a stain streak inside its usable area where a 2A board cannot. 2A is the backbone of the hardwood flooring industry and is good for short, painted or hidden parts. No. 3A and No. 3B at 33-1/3 and 25 percent are pallet, crating, blocking and shop-shorts grades.

What FAS also limits, beyond yield

Yield and cutting count are the headline, but the FAS rule also caps individual defects, and these are worth knowing because they are what you are really paying the premium for. The limits below are expressed against surface measure, so they scale with the board.

Softwood Grades: Appearance versus Strength

Softwood grading runs under a different set of agencies: the Western Wood Products Association in the West, the Southern Pine Inspection Bureau in the South, NELMA in the Northeast and others, all accredited under the American Lumber Standard Committee, which enforces the US Product Standard PS 20. The names below are WWPA designations. Other regions use their own labels, so read them as the WWPA system rather than as universal law.

Appearance and board grades, graded for looks

The clean, near-clear boards you buy for trim and shelving are Selects. WWPA rolls its top two levels into B & Better Select, essentially clear, for fine furniture and natural-finish trim. C Select, also named CHOICE, has small tight knots and a near-perfect face. D Select, or QUALITY, carries more small knots and minor blemishes. A separate premium Finish ladder, usually available only in Douglas fir, runs SUPERIOR, PRIME, then E.

The knotty board grades, mostly pines, spruces and cedars, pair a number with an official WWPA descriptive name, one to one. These are real designations, not marketing.

Structural and dimension grades, graded for strength

This is the family stamped on the 2x material you frame with, and it is a strength classification. A mill grader assigns it by limiting knot size, slope of grain, checks and wane, and each grade maps to published design values: bending, tension, shear, compression and modulus of elasticity. From highest to lowest, the joists-and-planks ladder runs Select Structural, then No. 1 (with "No. 1 & Better" offered in Douglas Fir-Larch and Hem-Fir), then No. 2, which is the everyday framing grade and most of what you will buy, then No. 3. Light framing and studs add Construction, Standard, Utility and a dedicated Stud grade optimised for straightness in a wall.

Because these are strength grades, a knot near the edge of a board, or on the tension face, which is the stretched underside of a loaded beam, is restricted far harder than the same knot in the middle. Appearance grades do not think this way at all. That single difference in philosophy is why a board can be ugly and strong, or pretty and weak.

What a Grade Actually Buys You

Now the question nobody answers. You are standing in front of a rack where Select Structural costs meaningfully more than No. 2. What do you get for the money?

The honest answer is: it depends entirely on which failure you are designing against, and the two properties that matter move at completely different rates.

Grading knocks down two published numbers. Bending strength is how much load the piece carries before it breaks. Modulus of elasticity, written E, is stiffness, and it governs how far the piece sags long before it is anywhere near breaking. A grader's restrictions punish those two very differently, because knots and grain deviation interrupt the tension fibres that resist rupture much more than they change the average stiffness of the whole cross-section.

Here is what that looks like as a ratio against the top grade of the same species. I am publishing these as percentages rather than as psi values on purpose. This site does not reproduce the copyrighted design value tables, as our engineering methodology page explains; a ratio is a derived fact and it happens to be the more useful form anyway, because the question you are asking at the rack is comparative.

Read the pattern rather than the individual rows. Across every species group, dropping from Select Structural to No. 2 costs somewhere between 30 and 53 percent of the bending value but only 7 to 22 percent of the stiffness. Strength falls two to four times faster than stiffness does. Spruce-Pine-Fir is the extreme case: the common No. 1/No. 2 grade gives up nearly a third of its bending value while keeping 93 percent of its stiffness.

The rule this gives you

Match the grade to the property that governs your part, not to your anxiety.

This is not a theoretical distinction. It is the reason our shelf sag calculator asks for a species and a section but does not agonise over grade: on a shelf, sag is the limit and the grade barely moves the answer. It is equally the reason the deck builder and the stair calculator care a great deal about grade, because a joist and a stringer are strength-governed members. Same wood, opposite advice, and the ratio table above is why.

Reading a Grade Stamp

Every ALSC-accredited softwood stamp carries five things. Learn to read them and a pile of framing lumber tells you its own story.

• Certification and grading-agency mark. The logo of the accredited agency that supervised grading, for example WWPA, SPIB or NELMA. It certifies the rules were applied under ALSC oversight.
• Mill number or mill brand. Identifies the mill that produced and stamped the piece.
• Grade designation. The grade name, number or abbreviation, such as SEL STR, No. 2, STAND or STUD.
• Species or species group. A single species or a combination. The common groups are DF-L for Douglas Fir-Larch, HEM-FIR, SPF for Spruce-Pine-Fir and SYP for Southern Yellow Pine. The group matters because design values are published by group, not by individual tree.
• Moisture condition at surfacing. S-GRN is surfaced green, over 19 percent moisture, and it will shrink as it dries. S-DRY is surfaced dry at 19 percent maximum and is the most common. MC15 or KD-15 is 15 percent maximum. KD is kiln dried and KD-HT adds heat treatment for pest regulations.

An NHLA hardwood board carries nothing like this. Hardwood is graded and tallied by a person at the yard, so you inspect it yourself rather than reading its history off a printed mark. That asymmetry surprises people who move from framing into furniture work.

Rough, S2S, S4S, and the Quarter System

Grade tells you the wood's quality. Surfacing tells you how far the mill took it toward finished, and it changes both what you pay and what you actually receive.

The hardwood quarter system

Hardwood thickness is quoted in quarters of an inch, based on the rough sawn thickness. So 4/4, said "four quarter," is rough 1 inch, and 8/4 is rough 2 inches. The surfaced figures are not shop lore. They come from one NHLA rule: subtract 3/16 inch from the rough thickness for stock 1-1/2 inches and under, and 1/4 inch for stock over 1-1/2 inches. That single rule generates the entire table.

Softwood nominal versus actual

Softwood plays a different game. A 2x4 is not 2 inches by 4 inches and has not been for a century. The nominal name refers to the rough green dimension; the actual size is what survives drying and surfacing, and it is fixed by PS 20.

How to Calculate Board Feet

Hardwood is priced by the board foot, so you should be able to figure it before the yard does. One board foot is 144 cubic inches: a piece 1 inch thick by 12 inches wide by 12 inches long. It is a volume, not an area.

Here is the pricing nuance that catches people. Hardwood board footage is figured on the rough quarter thickness, not the surfaced thickness. A 4/4 board planed to 13/16 inch is still billed as 1 inch. You pay for the wood the mill removed. A rough board measuring 1-1/8 inch rounds up and bills as 5/4; a rough 1-5/8 bills as 6/4. Width has an NHLA rule too: surface-measure fractions below the half foot drop, fractions above round up, and an exact half is counted alternately up then down from board to board so it averages out across a pack.

That is exactly why hardwood is sold rough by the board foot. The yard sells you a volume of rough wood; what you net after milling is your problem. Which leads directly to the question of which grade is actually cheaper.

Which grade is actually cheaper for your cut list

A grade's price per board foot is not its cost per usable board foot. Divide by the yield and the ranking can invert:

But the naive version of that calculation is misleading, and this is the part worth understanding. It assumes you can use every clear cutting the grade guarantees. You cannot, if your parts are longer than the grade's minimum cutting size. No. 1 Common only promises clear pieces down to 3" by 3' or 4" by 2'. If your longest part is 30 inches, that promise covers you and you realise close to the full 66-2/3 percent. If your parts are 5 feet long, many of No. 1 Common's guaranteed cuttings are simply too short to use, your effective yield collapses well below the nominal figure, and FAS pulls ahead despite costing more per board foot.

So the decision is driven by part length, not by budget or by pride. Sort your cut list, find the longest clear piece you need, and compare it against the minimum cutting size of the grade you were about to buy. If your longest part fits inside the lower grade's minimum cutting, buy the lower grade. If it does not, the higher grade is genuinely cheaper per usable foot even though the sticker says otherwise.

Spotting Defects That Matter

This is where a buyer earns the money back. Most guides blur check, shake and split together. I will not, because they behave differently and only one of them is usually a dealbreaker.

The separation trio: check, shake, split

A check is a lengthwise crack that runs along the grain and across the growth rings, caused by drying stress when the surface dries and shrinks faster than the core. It does not pass through the full thickness. Surface checks show on the face; end checks show on the fast-drying ends. A check is a seasoning defect, born after the tree was cut, and you can often plane or cut past a shallow one.

A shake is a separation parallel to the growth rings, either within a ring or between two adjacent rings, and it originates in the standing living tree. On cause, be careful with the old vocabulary. Grading language names shake by its supposed origin, so ring shake is also called wind shake or cup shake, and heart or star shake radiates from the pith. Older texts blamed wind, growth stress or frost. Modern wood science largely disagrees: SPIB, citing Dr. Gene Wengert, attributes the overwhelming majority of shake to anaerobic bacteria, the wetwood infection, entering through the roots and weakening the wood over decades. The name "wind shake" survives; the explanation behind it does not. What matters to you is that a shake can hide inside the board, invisible on the surface, and open up under load or after further drying. Because it separates whole growth rings, it is a bigger structural concern than a check.

A split goes all the way through the thickness, separating the piece along the grain. Splits are usually mechanical, from rough handling, dropping or an over-driven fastener, or they are a check or shake that has propagated through. Full thickness is the defining line: a check that breaks through becomes a split.

Knots

A knot is the base of a branch, embedded where the trunk grew around it. A sound, tight, intergrown knot, sometimes called a red knot, grew while the branch was alive, so its fibres are continuous with the surrounding wood. It stays put and carries some stress. A loose, dead, encased knot, a black knot, grew while the branch was dead, so the trunk grew around it without bonding. Its fibres are not continuous, it loosens as the board dries, and it can fall out and leave a hole.

What drives the grade is size, location and soundness together. Fibre deflects around a knot, so a knot interrupts the straight-grain load path. A knot on the edge of a member, or on the tension face, is far more damaging than the same knot in the centre, because it creates an eccentricity and a stress riser exactly where the fibres are working hardest. Strength grading restricts edge knots severely. For appearance work the priority reverses, and a big tight knot dead centre on a rustic tabletop is a feature.

The rest of the catalogue, and warp

Wane is bark or missing wood along an edge, where the board was cut near the outside of the log. It costs usable width and squareness. Pith is the soft, spongy centre of the original tree; wood at or around it is unstable and prone to checking, and boxed-heart boards that contain it move and split badly. Honeycomb is internal checking that opens inside the board during drying, often invisible on the face and revealed only when you cut or plane into it. It is irreversible, and a honeycombed board can look perfect and fall apart at the crosscut.

The warp family is any deviation from a flat, straight, true plane.

Bow is a curve along the length on the face, so the ends lift while the middle stays down; sight down the face to find it. Crook, also called crown, is a curve along the length on the edge, bending the board sideways in plane; sight down the edge. Framers deliberately install a crowned joist crown up. Cup is a curve across the width, the most common warp, and boards tend to cup away from the bark side. Twist, also called wind and said like winding a clock, throws the two ends into different planes so the board rocks on diagonal corners. Twist is the hardest to correct and the most wasteful to flatten.

Buying triage

• Sight down every board. Hold one end to your eye and look down the face to catch bow and cup, then down the edge to catch crook and twist. A board that rocks on a flat surface is twisted.
• Know where defects hurt. The tension face and the edges of any load-bearing part, the show face of anything exposed, and anywhere you cut a joint. A defect you can crosscut away between parts is nearly free. A defect running through your one clear rail is not.
• Separate cosmetic from structural. Small tight knots, mild colour streaks, minor surface checks and a little wane you can rip off are cosmetic and negotiable. Shake, honeycomb, pith, loose or dead knots on a tension edge and through-splits are structural. For a painted or rustic piece your tolerance rises; for a clear-finished heirloom or a load-bearing member it drops to near zero.

Frequently Asked Questions