The calculation determines how many 'effective part lengths' fit into the stock length.

1. Define Effective Part Length: The true length needed for each part is its finished length plus the width of one saw cut (kerf). This accounts for the material lost during the cut.
2. Calculate Piece Count: The calculator divides the total stock length by this effective part length and takes the whole number (rounding down) to find how many full pieces can be cut.
   Piece Count = Floor( Stock Length / (Part Length + Kerf) )
3. Calculate Waste: It then calculates the total length used and subtracts it from the stock length to find the remaining waste or offcut.

The answer assumes every part is the same length, cut from clean, straight stock in one orientation. When a project mixes several part sizes on the same board, run the calculator once per size or move to a full cut-list tool that nests mixed lengths together.

Example 1: Legs from an 8-foot 4×4.
Stock 96″, part 18.5″, kerf 0.125″. Each cut "consumes" 18.625″. Floor(96 ÷ 18.625) = 5 pieces, leaving a small usable offcut. Five legs from one blank means one fewer board to buy.

Example 2: Drawer fronts from a 10-foot rail.
Stock 120″, part 23″, kerf 0.093″ (a thin plywood blade). Effective length 23.093″, so Floor(120 ÷ 23.093) = 5 fronts with a few inches left over — enough to know you're short of six before you start.

• Ignoring the last kerf: Cutting N pieces means N cuts from the stock, so the offcut already reflects the final cut. Trust the tool's add-back rather than subtracting one more kerf by hand.
• Guessing the kerf: A dull or thin-kerf blade removes less than a full-kerf 0.125″. Measure it once per blade and reuse that number.
• Forgetting grain and defects: The math assumes clean, straight, one-direction stock. Cupto, warp, and checking may force you to burn a few inches or drop a piece.
• No cleanup allowance: Rough ends must be squared first. Shorten the stock input by your squaring cut before counting pieces.

"I run the numbers for two or three board lengths before I buy. A 12-foot stick sometimes yields more of a given part than two 8-footers, and the offcuts line up better for the next job. The piece count is cheap to change on paper and expensive to change at the saw." — Production Cabinetmaker

"Cut the longest parts first when you're hand-nesting from one board, then use the leftover length for the small ones. The single-length answer here is the starting point; real cut lists mix part sizes on the same stick."

• Stock: The raw material board or piece that you will be cutting from.
• Part: The smaller, finished-size piece you intend to cut.
• Kerf: The width of material removed by the saw blade.
• Offcut: The piece of stock material that is left over after all full parts have been cut.
• Effective Part Length: The finished part length plus one kerf — the real amount of stock each cut consumes.
• Squaring Cut: The first trim that makes an end straight and square, shortening the usable stock before you start counting parts.