Deck Footing Calculator: Bag Count & Dig Depth
Pick a footing tube diameter to get concrete per hole, total bags needed, and dig depth below your local frost line.
bags = ceil(5.6 ÷ 0.6) × 6 footings = 60
How it works
A tube footing is a cylinder, so the concrete per hole is π × radius² × depth. Diameter is in inches and depth is in inches, so the calculator works in feet under the hood and returns cubic feet per hole. Multiply by the number of footings for the total, then divide by the bag yield and round up.
Bags round up per hole, not across the whole job — you mix and pour each footing before moving on, so a partial bag left over at one hole rarely carries to the next. That is why the total is the per-hole bag count times the number of footings.
Depth is set by your frost line, not by the load. The bottom of the footing has to sit below the depth to which the ground freezes, plus a few inches of bearing, or frost heave will lift the deck every winter. Your building department publishes the frost depth for your area.
per hole = π × (16 ÷ 24)² × (48 ÷ 12) = 5.6 cu ft
bags per hole = ceil(5.6 ÷ 0.6) = 10 → total = 10 × 6 = 60