Concrete Tube / Sonotube Calculator

Volume = pi x (5)^2 x 36 / 1728 = 2,827 cu in / 1728 = 1.635 cu ft. With 60-lb bags: ceil(1.635 / 0.45) = 4 bags.

Most residential deck posts use 8-12 inch diameter tubes. Your local building department or a structural engineer will specify the required diameter based on the load.

Extend below the local frost line plus 6 inches. Common depths are 36 inches in mid-climates and 48-60 inches in northern regions. Check local building codes.

Concrete weighs about 150 lb/cu ft. A 10-inch tube at 36 inches deep holds 1.64 cu ft x 150 = 246 lbs of concrete.

Volume = pi x (6)^2 x 48 / 1728 = 5,428 cu in / 1728 = 3.14 cu ft. With 80-lb bags (0.60 cu ft each): ceil(3.14 / 0.60) = 6 bags per tube.

Footings must extend below the local frost line. Add 6 inches below frost depth for the footing pad. A minimum 12-inch diameter is common for deck posts; your building permit will specify the required size and depth.

For most residential deck footings, rebar is optional. For structural posts or where specified by an engineer, use 1-2 pieces of #4 rebar (1/2 inch diameter) centered in the tube, extending 12 inches above grade to anchor into the post base hardware.

Yes. Up to about 2 cubic feet (4-5 bags of 60-lb mix) is manageable by hand. Above 4-5 bags per footing, rent a portable electric mixer. For many tubes, order a partial yard of ready-mix delivered with a pump truck for efficiency and consistency.