How to use repeated lumber cuts
What this calculation does
A repeated-cut layout counts identical parts on stock after a per-board end trim and kerf between cuts.
Measure stock, part length, kerf and end trim, then enter the total number of repeated parts.
Enter the measurements
- Stock length: Measure usable stock length before the entered trim.
- Part length: Enter the repeated finished part length.
- Parts needed: Count all required pieces.
- Kerf between adjacent parts: Enter blade width between adjacent pieces.
- Total end trim: Enter trim removed once from each board.
Formula and variables
n = floor((stock − trim + kerf) / (part + kerf)); boards = ceil(parts / n).
Pieces per board uses floor((stock−trim+kerf)÷(part+kerf)); boards round the required piece count upward. Offcut subtracts actual part lengths, kerfs and trim.
Read the result
Six parts fit on one board; seven parts need two boards. A full six-part board leaves 4.875 in after the declared trim and kerfs.
Worked example
Inputs: 96 in stock, 7×15 in parts, 0.125 in kerf, 0.5 in trim
- Capacity = floor((96−0.5+0.125)÷(15+0.125)) = 6 parts per board.
- Boards = ceil(7÷6) = 2; full-board offcut = 96−0.5−6×15−5×0.125 = 4.875 in.
Expected result: 6 parts per board; 2 boards
Frequently asked questions
Why does this example need two boards?
The first board holds six 15 in parts; the seventh part starts a second board.
Is this the same as mixed-length optimization?
No. This tool repeats one part length; the mixed-length planner handles different lengths.
Conditions, presets and technical notes
Equal part lengths and one stock length. Kerf is counted between adjacent parts; total end trim is explicit. Residual includes any uncut end; no mixed-length optimization guarantee.