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Concrete for deck footings

A 12-inch round footing at 36in depth (a common deck footing depth below frost line) uses about 4 bags of 80lb premix per footing. Multiply by your footing count.

Fresh patio concrete form with wheelbarrow and tools

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.