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Deck footing calculator
Enter the deck size and get the posts, footings and bags of post-set concrete. It uses the same calculation as the deck designer, with post spacing for your country.
- Posts
- 16
- Footings
- 16
- Concrete (20 kg bags)
- 48
Posts at most 1.8 m apart along each beam, three bags per footing. Freestanding deck, no steps.
Common questions
How many footings does a deck need?
One per post. Posts go along each beam at no more than the usual spacing: about 8 ft in the US and Canada, about 1.8 m in the UK and Ireland. Count the posts on each beam, including both ends, and add the beams together.
How many bags of concrete per deck post?
We allow three bags of post-set concrete per footing: 80 lb bags in the US and Canada, 20 kg bags in the UK and Ireland. Deep frost footings or wide pads need more, so check the hole size your local rules ask for.
Does a deck against the house need fewer posts?
Usually yes. The side fixed to the house sits on a ledger board, so there is no beam and no posts along that edge. The designer lets you set this and the count follows.
Is this a structural design?
No. It is a material count using common residential spacing. Footing depth, soil, frost line and loads are for you and your local building rules to confirm.
Get the whole list, not just the posts
The designer adds boards, joists, beams, steps, railing and fixings for the same deck, and shows where each post goes in 3D.
Free, no account. Nothing is priced until you add your own rates. See a sample pack
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