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Concrete Volume for Footings

Enter footing shape, size, and count. We’ll compute concrete volume with waste, bag count for your mix size, and optional cost.

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What we calculate

Three linked steps — the same sequence you see when you hit Calculate.

01

Hole

Shape and dimensions set the volume of one footing.

02

Volume

We multiply by count and add your waste percent.

03

Bags

Volume ÷ bag yield becomes your order list (plus optional cost).

Frequently asked questions

How is footing volume calculated?

Round holes use π × (diameter ÷ 2)² × depth. Rectangular footings use length × width × depth. Multiply by the number of identical footings, then add your waste percent.

How deep should a footing or post hole be?

Depth depends on frost line, soil, and load. Fence posts are often ⅓ of post height below grade; deck piers follow local code. This tool sizes concrete — not structural depth.

How many bags of concrete do I need?

We divide total volume (with waste) by the approximate yield of your bag size (e.g. an 80 lb bag ≈ 0.60 ft³). Yields vary by brand — check the bag.

When should I use ready-mix instead of bags?

Bags suit a handful of holes. Once you’re near or past about ½–1 cubic yard, ready-mix or a trailer usually saves time and mixing labor.

Why add a waste factor?

Irregular holes, spillage, and over-excavation eat volume. Five to ten percent is a common DIY buffer; rocky or sandy soil may need more.

Is this accurate enough to order materials?

It’s a solid planning estimate for identical footings. Odd shapes, belled piers, and sonotube walls change volume — confirm with a supplier before ordering a truck.