Concrete Footing Calculator

A concrete footing is the base layer poured into the ground to support a structure — and the Concrete Footing Calculator tells you exactly how much concrete you need before you order or mix. Select your footing type (rectangular/strip or circular/round), enter the length, width, and depth (or diameter for round footings), and set a waste factor to get your total concrete needed in cubic yards, cubic feet, and the number of 40 lb, 60 lb, and 80 lb bags required. Also try the Concrete Slab Calculator.

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Add extra concrete to account for waste and variations

Results

Concrete Needed

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Cubic Feet

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40 lb Bags

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60 lb Bags

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80 lb Bags

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Frequently Asked Questions

How do I calculate how much concrete I need for footings?

Calculate the volume by multiplying length × width × depth for rectangular footings, or use π × radius² × depth for circular footings. Convert to cubic yards by dividing by 27. See also our Post Hole Concrete Calculator.

What is the standard depth for concrete footings?

Footing depth typically ranges from 12-24 inches below the frost line. Most residential footings are 18-24 inches deep, but check local building codes for requirements in your area.

Should I order concrete by the yard or use bags?

For projects over 1 cubic yard, ready-mix concrete is usually more cost-effective and convenient. For smaller projects or DIY work, bagged concrete offers better control and no minimum orders.

How many 80 lb bags of concrete do I need per cubic yard?

You need approximately 45 bags of 80-pound concrete mix to make one cubic yard. Each 80 lb bag yields about 0.022 cubic yards when mixed. You might also find our Concrete Stairs Calculator useful.

Why should I add a waste factor to my concrete calculation?

A 5-10% waste factor accounts for spillage, over-excavation, and measurement variations. It ensures you have enough concrete to complete your project without delays.

What's the difference between strip footings and pad footings?

Strip footings are continuous foundations that support walls, while pad footings are isolated square or circular foundations that support individual columns or posts.

How wide should concrete footings be?

Footing width should typically be twice the wall thickness. For example, an 8-inch wall needs a 16-inch wide footing. Always consult local building codes for specific requirements.