Concrete Footing & Pier Calculator (Sonotube)
Calculate concrete cubic yards and pre-mixed 60lb/80lb bags for cylindrical Sonotube piers, post footings, and deck foundations with depth and diameter.
Calculated Results
Frequently Asked Questions
How deep should concrete deck footings be dug?
Footings must extend below the local frost line depth specified by municipal building codes (typically 36 to 48 inches in northern US states, and 12 to 24 inches in southern states) to prevent frost heaving from lifting and cracking the deck structure.
What size Sonotube cardboard form should I use?
A 10-inch diameter cylinder is standard for residential ground-level decks. For elevated decks, hot tub supports, or roofed porches, building codes frequently require 12-inch or 16-inch diameter piers to spread load across sufficient soil surface area.
How many 80 lb bags of concrete equal one cubic yard?
It takes exactly 45 bags of 80-pound concrete mix to yield one cubic yard of cured concrete (or 60 bags of 60-pound mix). Each 80-lb bag yields approximately 0.60 cubic feet.
Why use a flared base or plastic footing form at the bottom?
A flared bell base dramatically increases soil bearing surface area, preventing heavy deck piers from settling into loose soil while providing mechanical resistance against soil frost uplift.