Decking Boards
Calculator
Results
- Rows of boards
- 28
- Linear metres of board
- 154
- Deck area (m²)
- 20
Construction results
| Rows of boards | 28 |
| Linear metres of board | 154 |
| Deck area (m²) | 20 |
formula-map diagram
- Rows of boards
- 28
- Linear metres of board
- 154
- Deck area (m²)
- 20
Formula breakdown
Formula
rows = ceil(deck width ÷ (board width + gap)); linear m = rows × deck length × (1 + waste ÷ 100)= 28
Note
Simplified model: results are quantity estimates only. They ignore openings, overlaps, cuts, site conditions and local building codes. Structural figures are not a substitute for a design by a qualified engineer.
More in Construction and trades
See all →Frequently asked questions
How does the calculator determine how many deck boards are needed?+
It divides the deck's total area by the coverage of a single board (board width plus the gap left between boards for drainage and expansion), then factors in board length to determine how many linear boards, or what total linear footage, is required.
Why does the calculator ask about the gap between boards?+
The gap (commonly 1/8 to 1/4 inch) affects how much actual decking width is needed to cover a given area — wider gaps mean each board effectively covers slightly less area, so more boards (or more total linear footage) are needed to span the same deck size.
Does board orientation (parallel or perpendicular to the house) change the material needed?+
It changes board lengths needed and seam locations, but not the total area covered — however, running boards perpendicular to joists often requires fewer end-to-end seams if it aligns better with standard board lengths and the deck's long dimension, which can reduce waste from cutting.
How much waste allowance should I add for decking boards?+
A common allowance is 10%, covering cuts at the deck's edges, defects that need to be cut out, and the reality that board lengths rarely divide evenly into the deck dimension, leaving an offcut at the end of each run.
Should I calculate the substructure (joists, beams) separately from the decking boards?+
Yes — this calculator addresses the visible decking surface only; joists, beams, and posts are sized and spaced based on structural load requirements and span tables, which is a separate calculation from how many boards cover the walking surface.