Material calculator
Deck Board Calculator
Calculate decking boards for a simple rectangular deck with gap, length, waste, and optional cost.
These results are planning estimates only. Verify product labels, site conditions, local requirements, and professional guidance before buying or building.
Calculator inputs
Adjust the typical defaults below. Results update automatically.
Results
Review quantities, warnings, and the shopping list before buying.
Deck area
192sq ft
Board rows
35rows
Pieces per row
1pieces
Boards to buy
39boards
Material list
- 39 boards Deck boards12 ft stock length
- 192 sq ft Surface area
- Verify separately Fasteners, joists, beams, railingsNot included
Breakdown
| item | calculation | value | unit |
|---|---|---|---|
| Board module | (width + gap) / 12 | 0.469 | ft |
| Rows | Across-deck distance / board module, rounded up | 35 | |
| Pieces per row | Run length / stock board length, rounded up | 1 | |
| Raw boards | 35 | boards | |
| Waste included | 10 | % |
How to use
- Enter deck dimensions and board dimensions.
- Choose the direction boards run.
- Review board rows, pieces per row, and total boards to buy.
Input guide
- Board width and gap are entered in inches.
- Board length is the stock board length in feet.
- Price per board is optional and not live pricing.
Common mistakes
- Ignoring the gap between boards.
- Mixing up board run direction and deck width.
- Using this for joists, beams, footings, stairs, or railings.
Assumptions and limitations
- No joist span, beams, footings, stairs, railing, structural design, or code advice is included.
- The deck surface is treated as a simple rectangle.
- Waste is a percentage allowance, not an optimized cut plan.
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Formula
- Board module = board width + gap, converted to feet.
- Board rows = deck width across boards / board module, rounded up.
- Pieces per row = board run length / board length, rounded up.
- Boards to buy = rows x pieces per row x waste factor, rounded up.
Example
A 12 ft x 16 ft deck with 5.5 in boards, 0.125 in gaps, and 12 ft boards needs 35 rows and 2 pieces per row, or 77 boards with 10% waste.
FAQ
Does this calculate framing lumber?
No. It only estimates surface decking boards for a simple rectangular deck.
Should I include board gaps?
Yes. The gap changes how many rows fit across the deck width.