Concrete Volume Calculator

The concrete volume calculator computes the amount of concrete needed for slabs, footings, cylindrical columns, and walls. It provides results in cubic feet, cubic yards, and cubic meters, and converts the volume into the number of 40 lb, 60 lb, or 80 lb premix bags required, with an optional waste factor.

How the Concrete Volume Formulas Work

Each pour type uses a simple geometric volume formula:

• Slab: V = L × W × T (for flat horizontal pours like patios and driveways)
• Footing: V = L × W × D (for foundation strip footings)
• Column: V = π × r² × h (for cylindrical pours like Sonotube columns)
• Wall: V = L × H × T (for vertical foundation and retaining walls)

How to Use

Select the pour type and your preferred length and thickness units. Enter the dimensions of your pour. Choose a waste factor (10% is the recommended contractor default) and your preferred bag size. The calculator shows the total volume in cubic yards, cubic feet, and cubic meters, along with the exact number of bags needed (rounded up).

Bag Yield Reference

• 40 lb premix bag yields 0.30 ft³ (90 bags per cubic yard)
• 60 lb premix bag yields 0.45 ft³ (60 bags per cubic yard)
• 80 lb premix bag yields 0.60 ft³ (45 bags per cubic yard)

When to Use Ready-Mix vs Bags

For pours over 1.5 cubic yards, ordering ready-mix concrete is usually more economical and produces a stronger monolithic pour. Bagged premix is best for small projects under 1 cubic yard where a ready-mix truck minimum delivery would be wasteful.