About Concrete Calculator

Estimates concrete volume, bag count, cost, and total weight for four project types: slabs, footings, columns, and stairs. Supports feet or meters, configurable bag size (40/60/80 lb), adjustable waste factor, and custom cost per bag.

• Four project types with appropriate dimension inputs: slab (L×W×thickness), footing (L×W×depth), column (L×W×height), stairs (steps×width×height×depth)
• Automatic conversion from cubic feet to cubic yards for volume output
• Configurable waste factor (default 10%) added to calculated volume
• Bag size options: 40, 60, or 80 lb bags with bags-per-cubic-yard lookup
• Cost estimation based on custom price per bag
• Export results as JSON or copy as formatted text

Frequently Asked Questions

Why should I include a waste factor?

Concrete gets wasted through spillage, over-excavation, uneven subgrade, and formwork imperfections. 10% is a standard buffer for simple projects. Increase it to 15–20% for complex shapes, stairs, or remote pours where getting more concrete is costly.

When should I use bags vs. ready-mix delivery?

Bags are practical up to about 1 cubic yard (roughly 45 bags at 80 lb each). Beyond that, a ready-mix truck is cheaper and faster. This calculator is designed for bag-scale projects.