How this calculator works
The calculator sorts your pieces from longest to shortest and places each one on the first board with room left — a “first-fit decreasing” plan, which is close to the best possible for most project lists. Every cut removes the saw kerf, and each board loses the end trim you set. The result is how many boards to buy and what to cut from each.
Usable length = Board length − End trim
Each piece uses = Piece length + Kerf
Boards = boards needed when pieces are packed longest-first
Assumptions and tips
- All pieces come from the same profile (for example, all 2×4 or all 1×6). Make a separate list for each lumber size.
- Board lengths at lumber yards are often a little over nominal; this uses the nominal length to be safe.
Worked example
Using the default values in the calculator above:
| Input | Value |
|---|---|
| Board length you buy | 8 ft (96 in) |
| Saw kerf | 0.125 in |
| End trim per board | 0.5 in |
| Price per board (optional) | $0 |
| Result | Value |
|---|---|
| Boards to buy | 6 boards |
| Pieces | 16 |
| Material used by pieces | 83.7 % |
| Waste (kerf, trim and offcuts) | 16.3 % |
| Total length of pieces | 40.17 ft |
| Cost | $0 |
Cutting plan:
- Board 1: 60 + 24 in — offcut 11.25 in
- Board 2: 60 + 24 in — offcut 11.25 in
- Board 3: 36 + 36 + 18.5 in — offcut 4.63 in
- Board 4: 36 + 36 + 18.5 in — offcut 4.63 in
- Board 5: 24 + 24 + 24 + 18.5 in — offcut 4.5 in
- Board 6: 24 + 18.5 in — offcut 52.75 in
Step by step:
- Usable board length = 96 in − 0.5 in trim = 95.5 in
- Sort pieces longest first
- Place each piece on the first board with room; every cut uses 0.125 in of kerf
- Start a new board when no board has room
Common mistakes to avoid
- Forgetting kerf — eight cuts on one board lose a full inch.
- Mixing lumber sizes in one list; a 2×4 piece can’t come from a 1×6.
- Not buying a spare board for knots, splits and warps.
Frequently asked questions
How many 8 ft boards do I need?
Enter your piece lengths and quantities above — the cutting plan shows exactly how many boards and which pieces go on each.
What is saw kerf?
The width of material the blade turns into sawdust, usually about ⅛ in. Ten cuts lose over an inch.