A concrete calculator computes the volume of concrete needed for a rectangular slab based on length, width, and depth (thickness).
About this calculator
A concrete calculator computes the volume of concrete needed for a rectangular slab based on length, width, and depth (thickness). It converts the volume to cubic yards (the standard unit for ordering ready-mix concrete) and estimates the number of pre-mixed concrete bags needed.
Over-ordering concrete is wasteful; under-ordering causes delays. It lets you order the right amount with a small buffer for waste.
Common uses
- Estimate concrete needed for a driveway, patio, or walkway
- Calculate how many bags of pre-mixed concrete to buy
- Plan the concrete volume for a foundation slab
- Order ready-mix concrete in cubic yards
Frequently asked questions
How much concrete does a 60 lb bag yield?
A 60 lb bag of pre-mixed concrete yields approximately 0.45 cubic feet. An 80 lb bag yields approximately 0.60 cubic feet. A typical 10×10 ft slab at 4 inches thick requires 1.23 cubic yards, which equals about 74 bags of 60 lb or 56 bags of 80 lb concrete.