Decking Cost Calculator

Estimate the cost of a deck from the deck area, board price and optional joist, post and fixings costs.

Part of:Decking hub
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How to Use This Calculator

How to Use the Decking Cost Calculator

  1. Choose metric or imperial units and your currency.
  2. Enter the length and width of the deck to get its area.
  3. Add a waste allowance — 10% is typical to cover cuts and offcuts.
  4. Enter your decking board price per unit area. Optionally add a substructure cost (joists and posts) per unit area and a flat figure for fixings and extras.

How the Cost Is Worked Out

  • Deck area = length × width.
  • Decking cost = area × (1 + waste %) × your board price per unit area.
  • Substructure cost = area × your joist/post price per unit area.
  • Total = decking + substructure + fixings & extras.

Tips

  • Composite decking costs more per board than softwood but needs less maintenance — factor in long-term cost.
  • If your boards are priced individually, work out the price per square metre/foot first (board price ÷ board coverage).
  • This is a material estimate — add labour, balustrade and groundworks separately.

Common Questions

How much does decking cost per square metre?

It varies widely: budget softwood may be modest per square metre, while premium composite is several times more. Enter your own supplier price for an accurate figure.

Should I include the substructure in the cost?

Yes — joists, posts and footings are a real part of the cost. Use the optional substructure field to add them per unit area, or include them under fixings and extras.

Why add a waste allowance?

Boards rarely fit the deck exactly, so cuts and offcuts mean you buy more than the bare area. A 10% allowance covers most simple rectangular decks; complex shapes need more.

Does this include labour?

No. This calculator estimates materials only. If you are hiring a fitter, get a separate labour quote and add it to the total.

What is the biggest cost in building a deck?

Decking boards are usually the largest single cost, but the substructure of joists, posts and footings can add 30–50% on top. The calculator lets you include these.

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