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Decking Calculator
Calculate decking boards needed
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Result
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What this calculator does
Counts deck boards from deck area, board width and board length.
How to use it
- Enter deck width and length.
- Enter board width in centimeters and board length in meters.
- Set waste and read the number of boards.
Formula
boardArea = (Board Width/100) × Board Length boards = roundUp( Width × Length / boardArea × (1 + Waste Margin (%) / 100) )
Formulas are shown in metric units, exactly as the calculator computes them. Imperial entries are converted to metric first. Waste is applied as a multiplier (1 + waste/100).
Areas are in m² and volumes in m³. Centimeters are divided by 100 to give meters. RoundUp means the next whole piece or bag.
Variables
| Variable | Unit | Default |
|---|---|---|
| Width | m | 4 |
| Length | m | 5 |
| Board Width | cm | 14 |
| Board Length | m | 3.6 |
| Waste Margin (%) | % | 10 |
Worked example
Using the default values of this calculator (Width = 4 m, Length = 5 m, Board Width = 14 cm, Board Length = 3.6 m, Waste Margin (%) = 10 %), the calculator returns:
boardArea = (14/100) × 3.6 boards = roundUp( 4 × 5 / boardArea × (1 + 10 / 100) )
- Decking Boards: 44 boards
Assumptions and limitations
- Gaps between boards are not included in board width.
- Joists, fixings and board orientation are not modelled; boards must be cut to fit.
Waste, rounding and buying
Boards are sold in fixed lengths; choose a length that reduces offcuts. Order a few extra for warped boards.
Frequently asked questions
- Should I include the gap between boards?
- Add the gap to the board width to account for it.
- Does this include the frame?
- No. Only surface boards are counted.