Decking Calculator
Boards, joists and screws for a deck measured in metres and millimetres.
Works in your browser. Nothing you type is sent to us.
The deck
Boards usually run parallel to the house, across the joists. Fractions like 12 1/2 work.
Decking boards
Frame
Prices optional
| Item | Quantity | Note |
|---|
Counts cover the deck surface and the joists under it. Beams, posts, footings, ledger, stairs and railings depend on the design and your code; add them from the drawings. Worked out in your browser, nothing you type is sent to us.
Decking Calculator at a glance
- Price
- Free
- Data sent to us
- None, it runs in your browser
- Sign-up
- Not needed
- Counts
- Boards, joists, rim joists, screws or clips, fascia
- Units
- ft and in with fractions, or m and mm
- Not counted
- Beams, posts, footings, stairs, railings
How to use Decking Calculator
- Type the deck sizeLength is the way the boards run, width is the way the joists run. Fractions like 12 1/2 work.
- Choose the boards and framePick the board, the gap, the board length you will buy and the joist spacing, and tick fascia or diagonal if they apply.
- Read the listThe boards, joists, fixings and fascia update as you type. Add prices to see the cost of what you priced.
Type the deck's length and width in metres, choose 90, 120 or 140 mm boards or your own width, the gap, the board length you will buy and joist centres of 400, 450 or 600 mm, and read the number of boards, joists, rim joists, screws or clips and fascia with 10% added for cuts. Switch to feet and inches at any time; the measurements convert.
How it works
Decking Calculator is a web page that does its work on your own device. Everything you type or choose is worked out by your browser and never sent to a server, so nothing is stored and there is nothing to delete. There is no account, no sign-up and no limit on how often you use it.
Joist centres
Softwood decking boards 28 to 32 mm thick are usually laid on joists at 400 or 450 mm centres; composite boards state their own maximum, often 300 to 400 mm; 600 mm is only for thick hardwood boards rated for it. Check the board maker's span table and your local building rules.
Questions
How many decking boards for a 5 by 3.6 m deck?
In 140 mm boards with a 5 mm gap, 3.6 m divided by 145 mm is 25 rows, each one 5.4 m board cut to length, so 28 boards with 10% waste. Change the board length you buy and the count updates.
Other shortcuts
Deck Material Calculator · Deck Board Calculator
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