Concrete Calculator — Free 2026
Calculate exactly how much concrete you need for slabs, columns and stairs. Get results in cubic yards, cubic feet and bags.
How It Works
- Select the shape
- Enter dimensions
- Read your results
Understanding Concrete Volume Calculations
Whether you are pouring a patio slab, setting fence posts, or building stairs, accurately estimating concrete volume saves money and prevents waste. Concrete is sold by the cubic yard for ready-mix trucks and by the bag for smaller projects. This calculator handles the most common shapes and converts between all standard units automatically.
Slab Calculations
For rectangular slabs — patios, sidewalks, driveways, and garage floors — the formula is straightforward: multiply length by width by depth. The critical detail is converting depth from inches to feet before multiplying. A standard 4-inch slab is just one-third of a foot deep. For larger area calculations, use our square footage calculator to determine the surface area first.
Column and Stairs Calculations
Cylindrical columns use the formula pi times radius squared times height. This calculator handles the inch-to-foot conversion for diameter automatically. For stairs, each step is treated as a rectangular block (width times run times rise), and the volumes are summed across all steps plus a base slab. Always add 5-10% extra material to account for waste, spillage, and form irregularities.
Bags vs. Ready-Mix
For projects under 1 cubic yard, pre-mixed bags are practical. A 60-lb bag yields about 0.45 cubic feet and an 80-lb bag about 0.6 cubic feet of mixed concrete. For larger pours, a ready-mix truck delivery is more cost-effective and ensures consistent mixing. Most suppliers have a minimum order of 1 cubic yard. Use our unit converter to translate between metric and imperial measurements.
Comments