Concrete Calculator

Multiply slab length by width by thickness, using consistent units. For imperial measurements, convert thickness from inches to feet before multiplying. The calculator handles this conversion and adds your selected waste allowance.

Divide the total required cubic feet by the approximate yield of one bag, then round up. Typical yields are about 0.30 ft³ for 40 lb, 0.45 ft³ for 60 lb, and 0.60 ft³ for 80 lb bags. Always confirm the package yield.

Yes. Choose Post hole, enter the round hole diameter, hole depth, and number of fence posts. The calculator applies the cylinder formula to all holes, adds the selected waste allowance, and converts the result into whole bag estimates using the bag yield you choose.

For a round fence-post hole, the concrete volume is pi times radius squared times hole depth. The quantity per post therefore depends on the actual hole diameter and depth, not only the post size. Enter one hole and one post to see the per-post amount, or enter the full post count for the project total.

Divide cubic feet by 27 because one cubic yard contains 27 cubic feet. For example, 54 cubic feet equals 2 cubic yards.

Ten percent is a practical planning allowance for many small pours. A well-formed, level project may need less, while uneven excavation, spillage, or uncertain dimensions may justify 15 percent.

Thickness depends on loading, reinforcement, base preparation, soil, and local code. Four inches is common for many residential walkways and patios, but vehicle slabs or structural work may require a different engineered specification.

Use feet with inches for imperial projects or meters with centimeters for metric projects. Results are shown together in cubic feet, cubic yards, and cubic meters.