Concrete Calculator
Calculate cubic yards of concrete for slabs, footings, and columns.
About This Tool
When to Use This Calculator
Use the Concrete Calculator when planning any concrete pour — footings, slab foundations, sidewalks, patios, post holes, or column piers. Whether you are ordering ready-mix by the cubic yard from a batch plant or buying pre-mixed bags for a smaller project, getting the volume right prevents costly short-pours and excessive waste.
How It Works
Enter the dimensions for rectangular slabs or cylindrical piers and the calculator converts everything to cubic yards, the standard ordering unit for ready-mix concrete. It also estimates the number of pre-mixed bags needed for smaller jobs and can factor in a waste allowance for uneven subgrades, form bulging, and spillage that inevitably happens during a pour.
Tips for Best Results
- Always order 5–10% extra concrete to account for subgrade irregularities, form bulging, and spillage — running short mid-pour creates cold joints that compromise structural integrity.
- Each 80-lb bag of pre-mixed concrete yields about 0.6 cubic feet. For anything over half a yard, ready-mix delivery is usually more economical and far less labor.
- Most batch plants have a minimum delivery of 1 cubic yard and charge a short-load fee for small orders, so consolidate multiple small pours into one delivery when possible.
- For post holes and piers, measure the actual hole diameter after digging — augers often cut slightly oversized, which increases volume more than you might expect on cylindrical shapes.