Ordering concrete for a project can be stressful because you don't want to end up short (which causes cold joints and structural weakness) or way over (which wastes money and materials). A concrete calculator helps you get the numbers right the first time.
Our Concrete Calculator supports five shapes: rectangular slabs, circular columns/holes, tubes (sonotubes), curbs and gutters, and stairs. You can pouring a patio, setting fence posts, or building steps, the tool calculates the volume in cubic meters, cubic yards, and cubic feet. It also estimates how many 80lb, 60lb, or 40kg bags you'll need.
Key Tips for Accurate Estimates
- Always add 10%: Account for spillage, uneven subgrades, and formwork bowing. It's cheaper to have a little leftover than to run out mid-pour.
- Measure in multiple spots: Use the average depth, not the planned depth. A 4-inch slab may actually be 3.5 inches in some spots and 4.5 in others.
- Use the quantity field: If you have multiple identical footings or columns, enter the count to get the total volume in one calculation.
When to Order Ready-Mix vs. Bags
For projects under 2 cubic yards, bags are usually more practical. An 80lb bag yields about 0.6 cubic feet - you'd need 45 bags for 1 cubic yard. For anything larger, ready-mix delivery saves significant labor. Most trucks carry about 10 cubic yards per load.
All calculations happen locally in your browser. Your measurements stay private.