Slabs and footings
Multiply length × width × thickness using the same unit for all three dimensions. Use the same formula for a rectangular strip footing.
Concrete Calculator
Find out how much concrete to buy for a slab, footing, or fence project. Get volume, bag count, and material cost in one place.
Estimate your pour
Your concrete estimate
How to calculate concrete
Round post holes
Multiply π × radius² × fill depth × number of holes. The post-hole result estimates the full hole volume before subtracting any post displacement.
Bags and ready-mix
Add your allowance, then divide the volume by the mixed yield per bag and round up. For ready-mix, confirm order increments and fees with your supplier.
Example for a patio slab
A 10 ft × 12 ft slab at 4 in thick takes 40 cubic feet before allowance. With 10% extra, plan for 44 cubic feet, about 1.63 cubic yards, or 74 bags yielding 0.60 cubic feet each.
What does the cost include?
The estimate multiplies your unit price by whole bags or by concrete volume including your allowance. Delivery, tax, labour, and supplier minimums are separate.
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