Deck Post and Footing Calculator

How to measure

Length runs along the house; width is how far the deck sticks out from the house.

Deck size

Length along the house

Width out from the house

Deck type

Framing

Maximum joist span

From your plan or span table. Sets how many beams the deck needs.

Maximum post spacing

Footings

Footing diameter

Footing depth

At least your local frost depth.

Posts and footings

3 posts

12 bags of 80 lb concrete (or 16 of 60 lb) for the footings

How the estimate was calculated
Beams	1 beam
Posts per beam	3
Concrete per footing	2.36 cu ft
Concrete for all footings	7.07 cu ft
80 lb bags	12 bags
60 lb bags	16 bags

A planning estimate. Allowed beam and joist spans and footing size depend on lumber, load and soil; footings must reach below your local frost depth. Check your plans with the building department.

See the formula, sources and worked examples on Matholio