Concrete
Concrete Slab Calculator
Estimate concrete volume in cubic feet and cubic yards, then estimate bag count from your chosen bag yield.
Concrete
Calculator inputs
Concrete Slab Calculator Results
Results update in your browser as you edit inputs.
Enter project dimensions to calculate material quantity.
Assumptions
- The slab is treated as a simple rectangle with even thickness.
- Base material, forms, reinforcement, vapor barrier, and finishing materials are not included.
- Bag yield must come from the bag label or your supplier.
- Any cost estimate uses only the unit price you enter. The site does not provide live, current, near-me, or store-specific material prices.
Formula
- Volume in cubic feet = length x width x thickness in feet.
- Cubic yards = cubic feet divided by 27.
- Waste-adjusted volume = volume x (1 + waste factor).
- Bags = waste-adjusted cubic feet divided by bag yield.
Example calculation
Example: 10 x 10 slab
A 10 ft by 10 ft slab at 4 in thick is about 33.33 cubic feet, or 1.23 cubic yards, before waste.
Common mistakes
- Entering slab thickness in feet instead of inches.
- Ignoring uneven excavation or overdig.
- Using bag count for a project better suited to ready-mix delivery.
FAQ
Does this calculate ready-mix truck pricing?
No. It estimates volume only. Any cost estimate uses your own entered bag price.
What bag yield should I enter?
Enter the cubic-foot yield printed on the concrete bag you plan to use.