Woodworking and lumber words, explained
The calculators on this site use the words lumberyards, carpenters and building inspectors use. If a label stops you, the meaning is probably below — one line each, in plain English, with a link to the calculator where the word matters.
Buying lumber
| Word | What it means |
|---|---|
| Board foot (bd ft) | A volume of wood: 144 cubic inches, the same as a board 1 in thick, 12 in wide and 1 ft long. Hardwood dealers and many lumberyards price by it. Thickness (in) × width (in) × length (ft) ÷ 12. |
| Linear foot | Just length — 1 ft of a board, whatever its width. Trim, decking and home-center boards are often priced this way or by the piece. |
| Nominal size | The name on the tag, like 2×4 or 1×12. It is roughly the size the board was sawn at before drying and planing. |
| Actual size | What your tape reads. A dry 2×4 is 1½ × 3½ in; a 1×12 is ¾ × 11¼ in. Plan cuts and joints on the actual size. |
| 4/4, 5/4, 8/4 (“four-quarter”) | Hardwood thickness in quarter inches, measured rough: 4/4 is 1 in, 5/4 is 1¼ in, 8/4 is 2 in. Planed smooth, a 4/4 board usually ends up around 13/16 in. |
| S4S / S2S | Surfaced (planed smooth) on four sides / on two faces. S4S boards are ready to use; S2S hardwood still has rough, uneven edges to rip straight. |
| Rough lumber | Straight from the sawmill: fuzzy faces, full thickness, not yet planed. Cheaper per board foot, but you lose some thickness and width getting it flat. |
| Grade stamp | The ink stamp on construction lumber that names the species group, grade (e.g. No. 2), moisture (KD = kiln dried) and the grading agency. Span tables are read from it. |
| KD / green | Kiln dried (dried to a set moisture) versus green (freshly sawn and still wet). Green wood shrinks as it dries. |
| Stick (of trim) | One piece of moulding as sold, often 8 ft or 16 ft long. |
Two quick worked examples: a 2×4 that is 8 ft long is 2 × 4 × 8 ÷ 12 = 5.33 board feet on its nominal size — see how many board feet in a 2x4x8 — while its actual cross-section is only 1½ × 3½ in, explained in what is the actual size of a 2x4.
Cutting and joinery
| Word | What it means |
|---|---|
| Kerf | The slot a saw blade cuts — the sliver of wood each cut turns to sawdust. About 1/8 in for a full-kerf blade, 3/32 in for a thin-kerf one. |
| Cut list | The list of every piece a project needs, with lengths and quantities. The cut list calculator turns it into boards to buy. |
| Offcut | The leftover piece at the end of a board after your parts are cut. |
| Miter | An angled cut across the face of a board, set by swinging the miter saw left or right. Two 45° miters make a 90° picture-frame corner. |
| Bevel | An angled cut through the thickness of a board, set by tilting the blade. Crown moulding cut flat on the saw needs both a miter and a bevel. |
| Compound cut | A cut that is a miter and a bevel at the same time. |
| Long point / short point | On a mitered piece, the tips of the longer (outside) and shorter (inside) edges. Measure and mark to the long point unless a calculator says otherwise. |
| Rabbet | A step cut along the edge of a board. In a picture frame it is the ledge the glass, art and backing sit in. |
| Dado | A flat-bottomed groove across the grain, e.g. to hold the end of a shelf. |
| Spring angle | How far crown moulding leans off the wall. Most home-center crown is 38° (labelled 52/38); some is 45°. |
| Cope | Shaping the end of one trim piece to the profile of the other at an inside corner, instead of mitering both. |
Angles are worked out for common cases in crown molding miter angle for a 90° inside corner and miter angle for an octagon.
Decks and framing
| Word | What it means |
|---|---|
| On center (o.c.) | Spacing measured from the middle of one joist, stud or rafter to the middle of the next. “16 in on center” is the usual spacing. |
| Joist | The boards that run under the decking or floor and carry it, set on edge side by side. |
| Ledger | The board bolted to the house that holds one end of the deck joists. |
| Beam | The heavy member (often two or three boards fastened together) resting on posts that holds up the joists away from the house. |
| Span | The open distance a joist or beam crosses between its supports. Overhang past the support is not part of the span. |
| Cantilever | The part of a joist or beam that sticks out past its last support. |
| Rim joist / band | The board across the ends of the joists that closes the frame. |
| Header | A beam over an opening (door, window, stairwell) or the board across the joist ends that a stair hangs from. |
| Hanger board | A board fastened below the deck’s rim or header that the tops of the stair stringers are attached to. |
| psf | Pounds per square foot — how deck and floor loads are stated. Deck span tables in the IRC assume a 40 psf live load (people, furniture) plus 10 psf dead load (the deck itself) unless you pick a snow load. |
| Plumb cut / level cut | A cut that will be vertical (plumb) or horizontal (level) once the board is installed at its slope — the two cuts that make each stringer notch or a rafter seat. |
| Birdsmouth | The notch in a rafter (a plumb cut plus a level seat cut) that lets it sit on the wall. |
| Hip / valley rafter | The rafter that runs diagonally from a wall corner up to the ridge (hip, an outside corner) or along an inside corner where two roofs meet (valley). See the hip and valley rafter calculator. |
| Jack rafter | A shortened common rafter that runs from the wall to a hip, or from a valley to the ridge. Each one is shorter than the last by the same “common difference”. |
| HAP (height above plate) | How much rafter sits above the wall plate at the birdsmouth — it sets how high the ridge ends up. |
The span words come together in 2x8 deck joist span at 16 inches on center.
Stairs
| Word | What it means |
|---|---|
| Stringer | The notched board under the steps that holds them up. Most deck stairs use three or more. |
| Riser | How tall each step is — also the upright board that can close the back of a step. |
| Tread | The part you step on, and how deep each notch is cut. |
| Nosing | The front edge of a tread that overhangs the step below, usually about ¾ to 1¼ in. |
| Throat | The solid wood left in a stringer below the notches. Too little and the stringer is weak. |
| Total rise | The height the whole stair climbs, from where the bottom step lands to the top of the deck boards. |
| Total run | How far the stair reaches out horizontally. |
| Grade | The ground surface. “Above grade” means height above the ground. |
| Landing | A flat platform at the top or bottom of a stair, or partway up a tall one. |
A worked example: stair stringers for a 3 ft high deck — measure the height, and the calculator says how many equal steps fit.
Firewood and logs
| Word | What it means |
|---|---|
| Cord | A stacked pile of firewood 4 ft high, 4 ft deep and 8 ft long: 128 cubic feet, air gaps included. It is the standard unit US weights-and-measures rules use for selling firewood. |
| Face cord | One 4 × 8 ft row of pieces of whatever length they are cut. With 16 in pieces it is a third of a cord. |
| Rick | A regional word, usually meaning a face cord — but it has no fixed size, so ask the seller for the dimensions. |
| Seasoned | Firewood that has dried long enough to burn well, usually six months or more after splitting. |
| Log rule (Doyle, Scribner, International) | Formulas that estimate the board feet a sawmill can cut from a log. They give different answers for the same log. |
The row-versus-cord difference is worked out in how much is a face cord of firewood.
Wood as a material
| Word | What it means |
|---|---|
| Moisture content (MC) | The weight of water in wood as a percentage of its dry weight. Wood for indoor furniture is usually dried to around 8% in most of the US (the Wood Handbook’s recommended average for interior use); freshly cut wood is far wetter — often well over 50%. |
| Wood movement | Wood swells and shrinks across its width as the air gets more or less humid, and hardly at all along its length. |
| Flat-sawn / quarter-sawn | How a board was cut from the log. Quarter-sawn boards move less across their width. |
| Sag / deflection | How far a shelf or beam bends down under load. |
TipNot sure which calculator you need? Start from the job: a bookshelf starts with the cut list, deck steps with the stair stringer calculator, a raised bed with the cut list for a 4×8 raised garden bed.
Frequently asked questions
What does 16 inches on center mean?
The distance from the middle of one joist, stud or rafter to the middle of the next is 16 in. Measuring center to center (rather than the gap between boards) keeps the spacing the same whatever the boards’ thickness.
What is the difference between a miter and a bevel cut?
A miter is angled across the board’s face — you swing the saw left or right. A bevel is angled through its thickness — you tilt the blade. A compound cut is both at once.
What does kerf mean in woodworking?
The width of the cut a saw blade makes — the wood it turns to sawdust. Allow for it between pieces: about 1/8 in for a typical full-kerf blade.
Sources
- NIST, Voluntary Product Standard PS 20-20, American Softwood Lumber Standard (Rev. 1, 2021) (opens in a new tab) — Nominal and dressed softwood lumber sizes; board measure.
- ICC — 2021 International Residential Code, Chapter 3 (R311.7 stairways) and Chapter 5 (R507 decks) (opens in a new tab) — Stair, deck, joist and load terms; Table R507.6 assumes 40 psf live load and 10 psf dead load.
- USDA Forest Products Laboratory — Wood Handbook (FPL-GTR-282, 2021) (opens in a new tab) — Moisture content, shrinkage and wood movement; Table 13-2 gives 8% as the recommended average moisture content for interior woodwork and furniture in most of the US.
- California Department of Food and Agriculture, Division of Measurement Standards — Firewood (opens in a new tab) — The 128 cu ft cord and how firewood may be sold.