FootingCalc

Free calculator

Deck Footing Calculator

Sonotube and pier footings: concrete per tube, total for the deck, and how many bags to buy.

Tube dimensions

Set depth below your local frost line — your building department publishes the requirement.

Concrete needed

0 BAGS (80 lb)
Per footing0 ft³
Bags per footing0
Total volume0 ft³
Total cubic yards0

Over ~1 yd³ total, price a short-load ready-mix delivery against the bag count before you buy.

Doing whole plans, not single runs?

FootingTakeoff reads a footing plan and returns total linear feet, pad count, and an invoice at your rates — automatically.

See FootingTakeoff

Tube math

ft³ per tube = π × (diameter ÷ 24)² × (depth ÷ 12)

Doubling the diameter quadruples the concrete — a 16″ tube takes 1.8× the concrete of a 12″ tube at the same depth. If your plan calls for a flared base or a square pad under the post, size the pad with the pad calculator and add it.

FAQ

Deck footing questions, answered.

How much concrete per deck footing?
A cylinder: pi x radius squared x depth. A 12 inch diameter tube 48 inches deep takes about 3.14 cubic feet — roughly 6 x 80 lb bags per footing. A 10 inch tube at 48 inches is about 2.2 cubic feet, or 4 bags.
How deep should deck footings be?
Below the local frost line, which varies from zero in warm climates to 4 feet or more in cold ones — your building department publishes the required depth. Footings that stop above frost heave and move the deck.
What diameter sonotube for a deck?
8-12 inch tubes are common for typical decks, sized by the post load and soil; bigger decks and point loads use larger tubes or a flared base. Follow your permit drawings or local deck code tables.
Bags or ready-mix for deck footings?
Bags win for a handful of tubes since trucks have minimum loads; a large deck with many footings can justify a short-load truck. Ten 12-inch x 48-inch tubes is about 1.2 cubic yards — right at the crossover.