Inputs
Example scenarios
Click Use to load values into the calculator.
| Scenario | L (ft) | W (ft) | Board L (ft) | Board W (in) | Gap (in) | Joist Sp. (in) | Orientation | |
|---|---|---|---|---|---|---|---|---|
| Patio deck | 16 | 12 | 12 | 5.5 | 0.25 | 16 | Along length | |
| Small square | 10 | 10 | 10 | 5.5 | 0.1875 | 16 | Along width | |
| Deep terrace | 24 | 14 | 16 | 5.5 | 0.25 | 12 | Along length |
Results
Deck area
—
square feet
Total board pieces
—
including waste
Boards lineal length
—
lineal feet
Estimated screws
—
assuming two per crossing
Joists count
—
optionally includes two rim joists
Joists lineal length
—
lineal feet
Itemized bill of materials
| Item | Spec | Quantity | Unit | Notes |
|---|
All counts rounded up to whole pieces where applicable.
Formulas used
- Deck area (ft²) = lengthft × widthft.
- Effective board coverage (in) = board_widthin + gapin.
- Rows = ⌈ cross_dimensionin ÷ effective_coveragein ⌉.
- Pieces per row = ⌈ along_dimensionft ÷ board_lengthft ⌉.
- Total boards = rows × pieces_per_row; with waste = ⌈ total_boards × (1 + waste%) ⌉.
- Joists count = ⌊ along_dimensionin ÷ joist_spacingin ⌋ + 1 (+2 rims when enabled).
- Screws = boards_with_waste × joists_count × fasteners_per_crossing.
Joists run perpendicular to deck boards; rim/band joists parallel to rims at ends.
How to use
- Enter deck dimensions and board size. Pick orientation.
- Set the gap between boards, joist spacing, and waste allowance.
- Choose whether to include two rim/band joists.
- Click Calculate. Review the KPIs and bill of materials.
- Export your results as CSV or PDF for sharing or quotes.
FAQs
Orientation swaps which deck side determines rows versus pieces per row. Joist direction also flips.
Common gaps are 3/16–1/4 inch for wood; verify manufacturer guidance for composites and local codes.
Yes, you can toggle inclusion of two rim/band joists at deck ends to reflect common practice.
We multiply boards by joist crossings and fasteners per crossing, typically two. Adjust the fasteners field to match your hardware choice.
This version targets field boards and joists. Add-ons like picture-framing, fascia, posts, and rails can be added in a future update.