—
NZ outdoor project planning
Decking Calculator NZBoards, cuts and a budget you can adjust
Plan your deck in metres, compare board directions and see exactly what to buy. Get board quantities, a cutting estimate and a budget using prices you can change.
NZ materialsCut-list estimateNo sign-up
Deck takeoff and cost estimate
Start with the shape and material.
Start with a rectangle and the usable stock length your supplier can provide. The calculator reuses short cuts between rows and separates cutting offcuts from extra spare boards.
Your planning takeoff
Decking estimate
NZD including GST.
Finished rectangular deck area.
Decking purchased—
Joist lines—
Materials subtotal—
Your board layout
Illustration only; board lines are simplified on large decks.
Compare the other direction
Your budget, item by item
| Item | NZD incl. GST |
|---|---|
| Total with contingency |
What to put on the quote brief
Decking calculator NZ guide
Know what you are buying before the first delivery.
This decking calculator works out rows, purchased boards, reusable crosscuts, joist lineal metres and screw or clip quantities. Rotate the board direction to compare how the purchasing quantity changes.
Enter actual board width and the gap specified for your product. Nominal timber sizes can differ from finished dimensions. Stock lengths shown are planning options; random-length timber and composite profiles may not be available in every listed length.
The budget adds boards, fixings, your frame and labour allowances, other quoted costs and contingency. Rates are editable examples rather than measured NZ market averages. All output totals include GST; choose whether your input prices include or exclude GST.
For an L-shaped deck, calculate its non-overlapping rectangular sections separately. The tool does not combine offcuts across separate estimates, and does not calculate diagonal decking, picture framing, member sizes or foundation design.
Common NZ questions
Decking calculator FAQ
How many decking boards do I need?
Rows = round up ((deck width in mm + gap) ÷ (board width + gap)). Multiply rows by the run length for net lineal metres. Stock board quantities also depend on usable length, reusable crosscuts and spare boards. For a 5m × 4m deck with 140mm boards and 6mm gaps, boards along the 5m length need 28 rows and 140 net lineal metres. With usable 5m stock and 10% spares, that is 31 boards.
What is the best joist spacing for a NZ deck?
BRANZ describes maximum centres of 450mm for 19mm timber decking and 600mm for 32mm decking in the relevant guidance. These are not universal permissions for all timber or composite products. The calculator starts at 450mm and lets you enter the spacing from your design and product installation guide.
How much does a deck cost per square metre in NZ?
Use supplier and builder quotes for your material, site and region. This calculator produces an itemised budget from editable example prices, not a measured regional price range. Height, access, foundations, barriers, stairs, design, finishing and demolition can substantially change the cost. Add quoted extras and contingency before comparing the total with a builder quote.
Does a deck need building consent in New Zealand?
Building work must comply with the Building Code. MBIE says a deck where it is possible to fall more than 1.5 metres generally needs a building consent, while an exemption may apply in other cases if its conditions are met. A safety barrier can still be required for a fall of one metre or more, and local planning rules may also apply. Check with your council.
Should I use 450mm or 600mm joist centres?
Use the spacing permitted for the thickness, species or composite product you have selected. Thinner boards generally need closer joists. The result is a material takeoff only; it does not size bearers, piles, connections or spans.
How much waste should I allow for decking?
The tool calculates stock-length cutting offcuts first, then adds the percentage you choose as whole spare boards. Ten percent is an editable planning starting point for defects and mistakes. It is not a substitute for measuring angles, picture frames or stairs. Crosscut reuse allows a 3mm saw cut but assumes no end trimming; confirm usable stock length.
Designed for real NZ decisions
The assumptions stay visible.
Boards
Rows include the final deck edge without adding an imaginary gap outside it. Short crosscuts can share stock boards, allowing a 3mm saw kerf. Extra spare boards are rounded up separately.
Framing
Joist lines include both edges, spaced no further apart than your entered centres. Rims, blocking, butt-joint supports, bearers, piles and member sizes need a separate design.
Budget
Board and fixing quantities use your unit prices. Frame and labour use your area allowances; extras and contingency are added once. Example rates are assumptions, not a survey of regional prices.
Sources and limits
Use the estimate with the right checks.
Checked 15 September 2026. Bunnings examples informed the starting board rates; fixed stock-length availability and product profiles must be checked. Frame, labour and fixing rates are editable illustrative allowances.
MBIE · Decks, platforms and bridges Building consent exemptions, 1.5m fall threshold and barrier guidanceStandards New Zealand · NZS 3604 advisory note Deck board thickness and joist-centre provisionsBRANZ · Slatted decking Common NZ board sizes, 12mm wall gap and durability contextBunnings NZ · Build a deck Practical planning guidance and 450mm joist-spacing explanationBunnings NZ · Decking product prices Illustrative retail per-lineal-metre prices to replace with your own quote