Concrete Bags Needed
Calculator

It divides your required concrete volume by the yield of a single bag at your chosen bag size — for example, a standard 80 lb bag yields about 0.6 cubic feet of mixed concrete, so dividing total cubic feet by 0.6 gives the bag count.

Concrete is dense (roughly 150 lb per cubic foot once mixed and cured), so a bag's dry weight converts to a proportionally small wet volume. This is a common surprise for first-time DIYers who underestimate how many bags a project actually needs.

Always round up, and add a buffer beyond that — partial bags can't be bought, and running short mid-pour risks a cold joint (a visible weak seam where old and new concrete meet). Most guidance suggests ordering 5-10% more bags than the raw calculation.

Bagged concrete is generally reasonable up to about 1-2 cubic yards; beyond that, both the cost per unit volume and the physical labor of mixing dozens of bags typically make ready-mix delivery from a truck more practical and often cheaper overall.

Yes, proportionally — a 40 lb bag yields about 0.3 cubic feet and a 60 lb bag about 0.45 cubic feet, roughly half and three-quarters of the 80 lb bag's 0.6 cubic feet respectively, since yield scales with the bag's weight.