Deck Footing Concrete Calculator
Round pier footings for decks: set the diameter and depth, tell it how many footings, and get yards plus bag counts.
Sizing quick guide
| Deck situation | Typical footing |
|---|---|
| Ground-level deck, normal soil | 10" dia |
| Standard raised deck | 12" dia |
| Tall deck / heavy loads / hot tub | 16–18" dia, engineered |
Frost depth is the law of the land here — dig below it, always, or the first winter will lift your work back out of the ground.
Common questions
How big should deck footings be?
Most residential decks use 10–12 inch diameter footings for typical post loads, sized up to 16–18 inches for tall decks, hot tubs, or poor soil. Your local code and the deck's tributary load decide — check the span tables in your permit packet.
How deep do deck footings need to be?
Below the frost line on undisturbed soil. That ranges from 12 inches in the South to 48+ inches in the upper Midwest and mountain states. Footings above frost depth will heave and rack the deck.
How many bags of concrete per deck footing?
A 12" footing at 42" deep takes about 2.75 cu ft — five 80 lb bags. Multiply the per-foot values in the table by your depth, or just use the calculator with your exact numbers.
Do deck footings need rebar?
Codes often don't require it for simple pier footings, but two vertical #4 bars cost a few dollars per footing and add real crack resistance. With a bigfoot/bell base, rebar tying pier to base is good practice.