Concrete Calculator
Estimate concrete volume in cubic yards and number of bags needed for slabs, footings, or columns.
How this is calculated
Volume = L × W × D (slab) or π × r² × H (column). Add waste %. 1 cu yd = 27 cu ft. 60 lb bag ≈ 0.45 cu ft.
Frequently Asked Questions About Concrete Calculator
A concrete calculator estimates the volume of concrete needed for construction projects in cubic yards and cubic meters, plus the number of bags required for the mix.
How much concrete do I need for a 10x10 slab?
For a 10x10 ft slab that's 4 inches thick, you need about 1.23 cubic yards. The formula is length × width × depth (in feet) / 27 (cubic feet per yard). Add waste margin (usually 10%) for a total of about 1.35 cubic yards.
What is waste percentage and why is it important?
Waste accounts for spillage, overflow, and imperfect mixing. Standard waste is 5-10%. Always add waste to your estimate to avoid running short mid-project. It's better to have leftover concrete than to need more halfway through.
How many bags of concrete do I need?
One 60 lb bag covers about 0.45 cubic feet, while one 80 lb bag covers about 0.6 cubic feet. This calculator converts your volume estimate to the number of bags. Buy bags from a concrete supplier or home improvement store.
What is the difference between a 60 lb and 80 lb bag?
An 80 lb bag contains more concrete material than a 60 lb bag, so it requires less water to mix. The 80 lb bag is denser and sets faster. Choose based on project needs: 60 lb bags are easier to handle, while 80 lb bags are more economical.
How do I calculate concrete for a column or post?
For cylindrical columns, the formula is: π × radius² × height. Convert measurements to the same units, calculate volume, then divide by 27 for cubic yards. This calculator does it automatically when you select "Column" mode.
Can I use this calculator for curved or irregular shapes?
This calculator handles rectangles and cylinders. For irregular shapes, break them into simpler shapes (rectangles, triangles, cylinders), calculate each part, and add together. Or contact a concrete supplier for help with custom shapes.