Footing Calculator
Concrete for continuous strip footings or round pier footings -- real cubic yards and bag counts from your dimensions.
Add up every run -- for a full perimeter that's all four sides.
Concrete needed
1.32 cubic yards
(35.6 cubic feet)
80lb bags needed
60 bags
Trench bottoms are rarely perfectly flat, so standard trade advice is to order about 10% extra for footings -- more than for a formed slab. Running short mid-pour on a footing means a cold joint in the one part of the structure that carries everything else.
Keep going
- Footings are one piece of a larger concrete pour; the concrete calculator covers the slab or flatwork that often sits on top of them. Concrete Calculator
- Strip and pier footings are almost always reinforced; the rebar calculator sizes the bar that runs through this footing. Rebar Calculator
Frequently Asked Questions
Why are width and depth in inches but length in feet?
Because that's how footings are actually specified and dug: a "16 by 8" footing means 16 inches wide and 8 inches deep, while the run is measured in feet along the trench. The calculator converts everything to cubic feet before giving you yards.
How much concrete for a 12-inch pier 36 inches deep?
A little under 2.4 cubic feet each, so an 80 lb bag (0.6 cubic feet) covers a quarter of one pier -- four bags per pier. For a deck with 6 piers that's 24 bags, which is where ready-mix starts to make sense.
Does this tell me how big my footing needs to be?
No -- it only calculates the concrete volume for dimensions you already have. Required footing size depends on soil bearing capacity, the load above it, and frost depth in your area, which is a code and engineering question. Your local building department's prescriptive tables or an engineer's spec give you the dimensions; this tells you how much to order.