Concrete Calculators & Planning Guides
Estimate concrete for slabs, patios, driveways, footings and post holes. Start with the complete Concrete Calculator for volume, ready-mix ordering and bag quantities, or choose the project group that matches your job.
Calculate the whole pour
Enter length, width and thickness once to compare net volume, waste-adjusted volume, ready-mix ordering quantity and common bag sizes.
Concrete Calculator
Calculate square footage, cubic feet, cubic yards, ready-mix order quantity, 40/50/60/80 lb bags and approximate concrete weight.
Open Concrete Calculator →Concrete quick answers
Use reference pages for common quantities, then use the calculators when exact project dimensions matter.
How Many Bags of Concrete Do I Need?
Compare 40, 50, 60 and 80 lb bag quantities for common slab sizes and thicknesses.
Read guide →Concrete Yards Chart
Quick cubic-yard estimates for common slab sizes at 4, 5 and 6 inches thick.
Read guide →Concrete Bags per Fence Post
Reference common post-hole sizes and 40, 60 and 80 lb bag quantities.
Read guide →Plan a 20×20 or 24×24 concrete slab
For a larger patio or pad, start with the 20×20 Concrete Slab Calculator or 24×24 Concrete Slab Calculator. Compare concrete volume at different thicknesses and bag quantities, then customize the dimensions for your project.
Measure → calculate → choose bags or ready-mix
Measure the concrete dimensions, confirm the intended thickness, and include a reasonable extra-material allowance for uneven excavation, spillage and variation. For larger pours, compare the waste-adjusted cubic-yard result with ready-mix delivery options. For smaller jobs, use the bag-count outputs. Always verify structural design, reinforcement, base preparation and local requirements separately.