The cut list and the buying list
Start from the drawing, not from the lumber rack. Write one line for each kind of part: the name, the quantity, the thickness, the width, the length, the material, which way the grain runs, and a note when a joint changed the length. Thickness × width × length, in that order, is the size you will cut. The note is where you can see that a shelf is longer than the opening, and why.
That list is not yet a shopping list. A bill of materials, or a materials list, is the stock the parts have to come out of. Solid wood becomes board feet, or a count of boards of a known length and width. Plywood and other sheet goods become a count of sheets of a stated thickness. The buying list is larger than the sum of the parts. Joinery adds wood to a part, the blade removes a kerf between parts, and planing a rough board down to the finished thickness means you bought the thicker one.
Keep the two lists side by side. The cut list is what you mark on the wood. The buying list is what you order. Mixing them is how a 36 inch stile gets promised out of a pile of offcuts that add up on paper and do not contain 36 inches in a row.
Final size, then milling, joinery, and kerf
The final size is the part as it sits in the finished piece: the opening it spans, the face you see, the thickness you plane to. The cut size is that part after the joints have been added and before the saw kerf, which is not part of either piece. Rough size is the blank you mill the cut size out of.
On solid stock, people commonly leave about ½ inch to 1 inch of extra length so both ends can be squared, and about ¼ inch to ½ inch of extra width so one edge can be jointed and the piece ripped to width. A bowed or twisted board needs more. The board decides. These are shop habits, not a measured average, and they are not a percent added at the end. Thickness is the other allowance: rough 4/4 is counted as 1 inch and is often surfaced toward 13/16 or ¾. The nominal and actual sizes guide is that chart. Sheet goods do not get a planer allowance. A plywood part is cut to the rectangle on the list.
Joinery is added to the length of the part that enters the joint. A tenon is longer than the shoulder-to-shoulder opening by the tenon on each end. A shelf housed in dados is longer than the clear opening by the depth of each dado. The side or the stile that receives the joint does not grow. A ¼ inch dado in ¾ inch stock leaves ½ inch under the cutter. A quarter inch is one third of that thickness, and it is a common place to start. The dado and rabbet calculator does that subtraction for the depth you type. It does not rate the shelf.
Saw kerf is the groove the teeth cut between two parts. A full-kerf table-saw blade is about ⅛ inch. A thin-kerf blade is closer to 3/32 inch. Measure a test cut in the same blade and the same material when the leftover is only a kerf or two. The kerf is not added to the length of each part. Between n pieces in a row there are n − 1 kerfs, and none after the last. The kerf and yield calculator is that count for identical lengths. Forgetting the last-piece rule makes the board look shorter than it is.
Board feet = thickness (in) × width (in) × length (in) × quantity ÷ 144
Use the thickness and width you are buying, and the length you will cut, including tenons and dado tongues. Then, if you want a defect allowance, multiply that volume. The board-foot guide uses ten to twenty percent for knots, sapwood, and offcuts, and it is explicit that the percent does not stretch a board. An extra inch of length belongs on the blank before you divide, or it does not get counted.
Group the parts, then cut
Group by material and thickness before you buy and before you set the saw. All the ¾ inch plywood is one group. All the 4/4 hardwood is another. A ¼ inch back, if the drawing has one, is a third group and usually another sheet. Parts in one group can share a machine setting and a board. A plywood side and a hardwood stile do not.
Inside a group, the long parts claim stock first. A short rail cut out of the middle of the only board that could have made the stile is how a list that added up fails at the saw. The linear cut list sorts mixed lengths longest first and then sets each piece on the first board that can hold it, with a kerf between pieces and none after the last. It is a buying estimate. A person standing at the rack can sometimes pack tighter, and that calculator says so.
Crosscut and rip are a sequence you choose. On solid stock a common order is to crosscut an awkward board down near the longest part so it will sit on the jointer, then joint a face and an edge, plane to thickness, rip to width, and crosscut to the length on the list. On a sheet, a common sequence is to rip strips at a width the parts share, then crosscut those strips to length. Crosscutting the sheet first is the other habit, used when the full sheet is hard to handle. Either way the kerf is the same slot. The sheet goods calculator places the rectangles; it does not choose which cut you make first.
Mark each piece as it leaves the saw. Name and length, on a face the joint will hide. Two rails of the same length are the same stick until one of them is marked top. Grain is a mark, too. Stiles that should match come off the same board, same face out. Plywood sides that should match stay a pair, and the face grain runs the way the drawing says. If a part must not be turned, lock it. The sheet layout will not rotate a locked part to save a sheet. Bookmatching a veneer is still a pencil mark. No formula does it.
A small bookcase
The drawing is an open bookcase, 24 inches wide and 36 inches tall, with no back and no doors. The case is ¾ inch plywood, 10 inches deep. A hardwood face frame, ¾ inch thick, is applied to the front, so the piece stands that much deeper than the plywood. The sides run the full height. The top, the bottom, and one shelf are housed in ¼ inch dados, one in each side.
Clear opening between the plywood sides: 24 − ¾ − ¾ = 22.5 inches. Each dado adds ¼ inch, so the three horizontal parts are cut 22.5 + ¼ + ¼ = 23 inches long. The sides stay 36 inches. The dados are cut into them.
| Part | Qty | Cut size | Grain |
|---|---|---|---|
| Side | 2 | ¾ × 10 × 36 in | Along the height |
| Top, bottom, shelf | 3 | ¾ × 10 × 23 in | Along the span |
The face frame finishes at the same 24 by 36 inches. Stiles are 1½ inches wide and the full height, so there is no tenon on their length. The opening between them is 24 − 1½ − 1½ = 21 inches, shoulder to shoulder. This example runs the tenon through the stile, so each tenon is 1½ inches, the full stile width, and the ends finish flush with the outside. The rail is cut 21 + 1½ + 1½ = 24 inches. A shorter tenon is the same addition with a smaller number: a ¾ inch stub on each end of that 21 inch opening is 22.5 inches, and it stops inside the stile. The buy below uses the through tenon.
| Part | Qty | Cut size | Counted as |
|---|---|---|---|
| Stile | 2 | ¾ × 1½ × 36 in | 1 × 2 × 36 in |
| Rail | 3 | ¾ × 1½ × 24 in | 1 × 2 × 24 in |
The counted size is the buying section, not a second cut length. Thickness is the rough 4/4 inch. Width is 2 inches: the 1½ inch face plus ½ inch, which is the top of the quarter-to-half-inch width allowance above. The lengths are the cut lengths. An extra ½ to 1 inch for squaring the ends is not on these lines yet.
From the cut list to the buy
At the finished ¾ by 1½ section, the stiles are ¾ × 1½ × 36 × 2 = 81 cubic inches, and 81 ÷ 144 = 0.5625 board feet. The rails are the same volume, because 24 × 3 equals 36 × 2: 81 ÷ 144 = 0.5625. Together that is 1.125 board feet. That is the wood left after planing and ripping.
At the rough section the two stile blanks are 1 × 2 × 36 × 2 ÷ 144 = 1 board foot, and the three rails are 1 × 2 × 24 × 3 ÷ 144 = 1 board foot. The face frame is 2 board feet before any defect allowance. Fifteen percent sits inside the ten to twenty percent the board-foot guide uses for knots, sapwood, and offcuts. On the board foot calculator that volume is 2 × 1.15 = 2.3 board feet. The percent does not add an inch to a stile.
If you itemize the ends instead, add the length before the division. One extra inch on a 1 × 2 blank is 1 × 2 × 1 ÷ 144 = 1/72 board foot. Five blanks add 5/72 board foot. Doing that and also adding 15 percent counts the ends in both places. Cut an inch long and the stiles are 37 inches, the rails 25. Two stiles are 74.125 inches and three rails are 75.25 inches, each group under 96, and the linear layout still wants 2 boards. Plywood is not cut long. Crosscut to the length on the list after the faces and edges are milled, from the longer strip. The list length is the finished length, tenons included.
Volume is not a board. The five cut lengths are 36 × 2 + 24 × 3 = 144 inches, which is already more than one 96 inch stick, before kerf. On 96 inch boards, ⅛ inch kerf, no end trim, both stiles take the first board: 36 + ⅛ + 36 = 72.125 inches, with 23.875 inches left. That remainder is shorter than a 24 inch rail. The three rails take the second board: 24 + ⅛ + 24 + ⅛ + 24 = 72.25 inches, with 23.75 inches left. Parts, kerfs, and leftovers add back to the boards you buy: 144 + 0.375 + 23.875 + 23.75 = 192.
| Board | Parts | Used | Left |
|---|---|---|---|
| First 96 in | Two stiles | 72.125 in | 23.875 in |
| Second 96 in | Three rails | 72.25 in | 23.75 in |
Both stiles are on the first board, so they can stay a matched pair. Mark left and right before they come apart. The three rails share a length, so the name is the only difference between top, middle, and bottom.
Two boards at a full 1 × 2 section, each 96 inches, are 1 × 2 × 96 × 2 ÷ 144 = 8/3 board feet. That is more than 2.3, because the leftovers are still on the sticks. Hardwood is often a wider board. One 4/4 board, 6 inches wide and 96 inches long, is 1 × 6 × 96 ÷ 144 = 4 board feet. Ripping 2 inch strips from it, the kerf calculator gets 2 strips when the kerf is ⅛ inch: 4.125 inches used, 1.875 inches left, which is short of another 2 inch strip. With the kerf set to zero the same 6 inches hold 3 strips, because 6 ÷ 2 = 3. The two real strips are the two 96 inch sticks above. This 4 board-foot board is a buy that contains the face frame. The 2.3 board feet are the volume check, not the order.
A thin-kerf blade, closer to 3/32 inch, still rips that 6 inch board into 2 strips, and the face frame still takes 2 boards. The leftovers move by a fraction. These counts do not.
The plywood is the other group. Every part is 10 inches in one direction. With the face grain running the 96 inch way, rip 10 inch strips and crosscut them. The 48 inch width holds 4 such strips at an ⅛ inch kerf. This case uses two. The sides share a strip: the kerf calculator puts 2 lengths of 36 on 96 inches, using 72.125 inches and leaving 23.875 inches. The three shelves share the other strip. Three of them are 23 × 3 + ⅛ × 2 = 69.25 inches, leaving 26.75 inches. That strip could have held 4 shelves. The case needs three. Across the sheet the two strips take 20.125 inches.
The rectangles are 1,410 square inches. A 48 × 96 sheet is 4,608. Area is not the proof they fit. The two strips are. The sheet calculator, rotation locked so the 10 inch edge runs across the 48 inch side, ⅛ inch kerf, no trim, reports 1 sheet for the same five rectangles. Its drawing is a shelf layout, not these two strips. The plywood guide is the case where four parts fill a sheet on area and need a second sheet once the kerf is real. This bookcase stays on one sheet.
Lock the other way, long edge along the 48 inch side, and the calculator still reports 1 sheet. Check the veneer on the sheet in front of you before you decide which axis is locked. Take ½ inch off every factory edge and the usable sheet is 47 inches across and 95 inches long. The side strip, the shelf strip, and the pair of strips still fit inside that, and the calculator with that trim still reports 1 sheet. A thin-kerf blade does not change the sheet count either: it stays 1.
| Buy | Arithmetic | Result |
|---|---|---|
| Finished face frame | 81 ÷ 144, twice | 1.125 board feet |
| Rough 1 × 2 blanks | 1 board foot + 1 board foot | 2 board feet |
| Those blanks, plus 15% | 2 × 1.15 | 2.3 board feet |
| Two 1 × 2 × 96 boards | 1 × 2 × 96 × 2 ÷ 144 | 8/3 board feet |
| One 1 × 6 × 96 board | 1 × 6 × 96 ÷ 144 | 4 board feet |
| ¾ plywood, 48 × 96 | The two strips above | 1 sheet |
Order the 6 inch board, or two sticks that are each at least 2 inches wide and 96 inches long, plus one sheet of ¾ inch plywood. Use 2.3 board feet only as a check that a pile of offcuts is in the right volume. An offcut still has to contain a 36 inch stile.
What a cut list will not decide
- It will not grade the board. A knot in the face of a stile still ruins that stick, including inside the 2.3 board feet.
- It will not say the ¼ inch dado is strong enough to carry the shelf. The dado page only tells you the ½ inch left under the cutter.
- It has no back, no doors, and no hardware. A back is another thickness and another group.
- The layouts are a checked way to fit these parts, the same kind of estimate as the calculators. They are the buy for this bookcase. They are not a rule for the next drawing.
Questions
Is a cut list the same thing as a bill of materials?
The cut list is every part, at the size you will cut, with the material and the grain. The bill of materials is the stock you buy so those parts can come out of it: board feet or whole boards of solid wood, and sheets of plywood. On the bookcase here the face-frame parts are 2 board feet before waste and 2.3 with 15 percent added. The 6 inch by 8 foot board that actually holds them is 4 board feet, and the plywood is a separate sheet.
Do I add the saw kerf to each part's length?
No. Kerf is the slot between two parts. Two 36 inch stiles on one board need one ⅛ inch kerf between them, not an extra ⅛ inch on each stile, and not a kerf after the last piece. The parts, that kerf, and the leftover are three different numbers. Adding the kerf to the part and then again between the parts counts it twice.
Which thickness goes into the board-foot line?
The thickness you are buying. These face-frame blanks are counted as 1 inch thick because rough 4/4 is an inch, even though they finish at ¾. Counted at the finished ¾ by 1½ they come to 1.125 board feet, which is the wood left after planing and ripping. Stopping the planer at 13/16 instead of ¾ does not change that buy. You already paid for the rough inch.
Why is 23.875 inches of leftover not a 24 inch rail?
Because 23.875 is shorter than 24. The ⅛ inch kerf between the two 36 inch stiles is what makes the remainder look almost long enough. Lengths that add up on paper still have to clear the tooth path. One 96 inch board cannot hold this list anyway: the five parts are 144 inches before any kerf.