Which concrete calculator do you need?
| Project | Use |
|---|---|
| Patio, shed pad, walkway, garage floor | Slab → Gravel base → Rebar |
| Wall or foundation footing | Footing → Rebar |
| Deck piers, Sonotubes, columns | Column / Sonotube, plus Footing for a wider base |
| Fence, mailbox or pergola posts | Post hole concrete |
| Entry steps | Steps |
| You already know the volume | Bags from volume |
Three numbers that come up again and again
- 27: cubic feet in a cubic yard. Divide ft³ by 27 to get the unit ready-mix is sold in.
- 0.60 ft³: the approximate yield of an 80 lb bag of Quikrete Concrete Mix (0.45 for 60 lb, 0.30 for 40 lb), per the manufacturer's data sheet. That's 45 bags of 80 lb mix per cubic yard.
- 5–10%: a typical waste allowance for flatwork, to cover uneven bases and spillage.
Bags or ready-mix?
Bags suit small pours, scattered post holes and places a truck can't reach. Once a job passes a cubic yard or two, a ready-mix delivery gives one consistent batch and saves hours of mixing. Ask local plants about minimum orders and short-load fees. Every calculator here shows both the cubic yards and the bag counts, so you can price either option.
Before you pour
Check local code for slab thickness, footing size and frost depth, call 811 before digging, and protect your skin: wet concrete is caustic (OSHA). Each calculator page covers the details for its project.