BuildTotals

Concrete for deck footings

A 12-inch round footing at 36in depth (a common deck footing depth below frost line) uses about 2 bags of 80lb premix per footing. Multiply by your footing count.

Material Totals

Concrete volume (with waste) 0.12 cu yd
80lb premix bags needed 6 bags
60lb premix bags needed 8 bags
Raw volume (no waste) 0.11 cu yd

1 cu yd = 27 cu ft. One 80lb bag covers ~0.6 cu ft; one 60lb bag ~0.45 cu ft. For pours over ~1 cu yd, ready-mix delivery is usually more economical.

This calculator treats footings as rectangular volumes. For a 12in (1ft) diameter round footing at 36in depth: pi x r^2 x depth = 3.14 x 0.5^2 x 3 = about 2.36 cu ft, which is about 4 bags. Use the calculator with 1x1 x 36in and adjust - or simply plan 2 bags per footing as a rule of thumb.

Check your local building code for required footing depth below the frost line. This varies significantly by climate zone.