| Deck (L×W) | Board width | Gap | Board length | Waste | Rows | Total board length | Boards | Screws |
|---|---|---|---|---|---|---|---|---|
| 12 ft × 10 ft | 5.5 in | 0.125 in | 12 ft | 10% | 21 | 287.3 ft | 24 | 696 |
Example numbers are illustrative and rounded.
- Rows across width:
rows = ceil(deck_width / (board_width + gap)) - Base board length:
base_length = rows × deck_length - Cutout adjustment (approx.):
cutout_length = cutout_area / board_width - Border (optional):
border_length = 2 × (deck_length + deck_width) - Pattern and waste:
final_length = (base − cutouts + border) × pattern_factor × (1 + waste%) - Boards to buy:
boards = ceil(final_length / stock_board_length) - Fasteners (approx.):
joists = floor(deck_length / joist_spacing) + 1, thenscrews ≈ rows × joists × screws_per_intersection
- Select a unit system, then enter deck length and width.
- Enter the actual board face width, desired gap, and stock board length.
- Choose straight or diagonal layout; diagonal usually needs more.
- Add waste percentage, and enable a border if needed.
- Optionally enter cutouts to subtract openings from the estimate.
- Set joist spacing and screw count per intersection for fasteners.
- Click Calculate to see results above the form.
- Download a CSV or PDF summary for records and suppliers.
Input measurements and units
Accurate deck length and width drive the estimate. The calculator accepts imperial or metric entries and converts them to a single internal scale for consistent results. Enter finished dimensions between outside framing edges, and subtract planned openings. If the deck is slightly out of square, use the larger measured side values so you do not underbuy.
Board coverage and row planning
Boards are assumed to run along the deck length, while rows are counted across the width. Row count equals deck width divided by the effective pitch, where pitch is board face width plus the gap. Wider boards reduce row count, while larger gaps increase it. The value is rounded up to ensure full coverage at the final edge, where trimming is typical.
Waste, diagonal layouts, and borders
Waste percentage covers end trimming, defects, and layout choices. Straight patterns often work with 8–12% waste, while diagonal layouts commonly need 10–15% because every course is cut at an angle and offcuts are harder to reuse. A picture-frame border adds perimeter length for a clean edge detail. Cutout areas reduce total board length using an area-to-length approximation.
Fastener planning for garden decks
Fastener count is estimated from board-to-joist intersections. Joist count is based on deck length and joist spacing, then multiplied by rows and screws per intersection. Two screws per joist is common for standard decking, but follow manufacturer guidance for composites or hidden systems. Add fastener waste to cover dropped screws and rework. Confirm fastener type and spacing with your framing plan.
Using exports for purchasing and records
CSV export lists inputs and results in a supplier-friendly format. PDF export creates a printable summary for onsite use and approvals. When buying materials, match the stock board length and actual face width to your entries, then adjust waste if you include breaker boards, stair nosing, or multiple cutouts. For staged deliveries, rerun the estimate after design changes to keep orders aligned with the latest layout and site conditions.
What board width should I enter?
Use the actual face width that will be visible after installation. For many “6-inch” boards, the true face can be about 5.5 inches. Measuring one board is best, especially for composites and grooved profiles.
How does the diagonal option change the result?
Diagonal layouts increase cutting and offcut waste. The calculator applies a diagonal factor to total board length, then adds your waste percentage. Use a higher factor when the deck is wide, has many edges, or uses multiple diagonal sections.
Should I include a border or picture-frame?
Enable the border option when you plan a perimeter frame or contrasting outline. It adds the deck perimeter to required board length, which helps prevent shortages. If your design uses mitered corners, consider adding a little extra waste.
How are cutouts handled?
Cutouts subtract area for features like planters, stair openings, or access hatches. The tool converts cutout area to an approximate board-length reduction. For complex shapes, break the opening into rectangles and use multiple cutout entries.
How do I adjust fasteners for hidden systems?
If you use hidden clips instead of screws, set screws per intersection to 1 and treat the result as an intersection count. Then convert intersections to clip quantities using your product’s spacing rules, and add fastener waste as needed.
Why do my board counts change when I tweak the gap?
Gap changes the effective pitch (board width plus spacing). A larger pitch reduces the number of rows, while a smaller pitch increases rows. Because the tool rounds up rows and boards, small changes can sometimes bump totals to the next whole board.