Outdoor
How Much Decking Do I Need?
Enter your deck footprint and board size. We return linear metres of board, joist count and fixings.
- 01Measure
- 02Adjust
- 03Result
- 04Shop
01 — Measure
Tell us about the job
Common: 12–15 cm
02 — Adjust
Material buffer
10% covers end cuts and board selection on longer runs.
Before you start — measure this
- Deck length
- Deck width
- Board width
- Joist spacing
03 — Result
137.5m
Decking board (linear)
- Deck area
- 17.5 m²
- Board rows
- 25
- Joists
- 14 × 3.5 m
- Screws
- ≈ 700
04 — Shopping list
Common: 3.0, 3.6, 4.8 m
39 × 3.6 m
- Total purchased
- 140.4 m
- Expected leftover
- 2.9 m
Optional — planning estimate, not a live price.
Stored in this browser only. No account needed.
How we got this number
- Deck area
- 17.5 m²
- Board pitch
- 14.5 cm
- Rows of board
- 25
- Linear board
- 125 m
- + 10% waste
- 137.5 m
Planning estimate: this calculation helps you estimate material quantities. Actual requirements vary with site conditions, product coverage, installation method and waste. Confirm with the manufacturer or a qualified professional when appropriate.
What to know about this material
- Leave a 5 mm gap between boards for drainage and timber movement.
- Composite decking expands more than timber — follow the maker's gap spec.
- Joists at 400 mm centres suit straight laying; drop to 300 mm for diagonal boards.
Frequently asked
- How many decking boards do I need?
- Divide the deck width by the board width plus gap to get rows, multiply by deck length for linear metres, then divide by your board length.
- What joist spacing should I use?
- 400 mm centres for boards laid square to the joists, 300 mm for diagonal patterns or thin boards.
- How many screws?
- Two per board per joist crossing — that adds up fast, so buy a full box.
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What this calculator answers
The highest-intent, lowest-competition searches this page is built to answer outright — every one of them is a quantity question you can settle above without leaving the page.
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Questions this page answers
This page is built around one job: estimate deck boards, joists and fixings for a given deck size.
- How many deck boards for a 12x16 deck?
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- How many screws per deck board?
- How much decking for a 200 square foot deck?
Also known as: deck board calculator, how much decking do i need, decking material estimator, joist calculator.