Concrete footing and sonotube estimator

Enter the tube diameter, the depth of each hole, and how many footings you are pouring. The estimator returns tube forms to buy, concrete volume for ready mix, and the 30 kg bag count. Bag counts use the epsilon safe ceiling BuildTrue applies everywhere. Switch between metric and imperial at any time. Your choice is remembered on this device. All results are estimates only.

Estimator

Tube diameter (mm)

Depth per footing (m)

Number of footings

Waste and overdig allowance (percent)

Formulas: volume per footing = pi x (diameter / 2) squared x depth. Total volume = volume per footing x number of footings. Volume with waste = total volume x (1 + waste / 100). Bags = ceiling of (volume with waste / 0.0135). Bag yield stated: one 30 kg pre-mix bag yields about 0.0135 cubic metres, the same yield the BuildTrue concrete estimator uses. Tube forms: one tube form per footing. 1 cubic metre = 1.30795 cubic yards.

Worked example: Tube diameter 12 in, depth 4 ft, 6 footings, waste 10 percent. Radius = 6 in = 0.5 ft. Volume per footing = 3.14159 x 0.5 x 0.5 x 4 = 3.14 cubic feet (0.089 cubic metres). Total volume = 3.14 x 6 = 18.85 cubic feet = 0.534 cubic metres. Volume with waste = 0.534 x 1.10 = 0.587 cubic metres (0.768 cubic yards). Bags = 0.587 / 0.0135 = 43.49, rounded up to 44 bags. Tube forms = 6, one per footing. The metric defaults, 304.8 mm diameter and 1.2192 m depth, are the exact equivalents of 12 in and 4 ft, so the defaults reproduce this example in both systems.

Estimates only. This is not engineering or code compliance advice. Frost depth, soil bearing, footing size, and inspection requirements are set locally. Verify with your building department and a qualified professional before digging or pouring.

Frequently asked questions

How deep should footings be in Canada?

Footings generally must extend below the local frost line so frost heave does not lift the structure. Frost depth varies widely across Canada, from under a metre to well over 1.8 m in colder regions. Your municipal building department publishes the required depth for your area. This estimator takes the depth you enter and does not set it for you.

Bags or ready mix for footings?

Bagged mix suits a few footings and tight access. Once a job passes roughly half a cubic metre, ready mix is usually faster and more consistent. The estimator shows both the bag count and the ready mix volume so you can compare.

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