Concrete Calculator
Figure out how much concrete you need for a slab, footing, or pad. Enter the dimensions to get the volume in cubic yards plus the number of 60 lb and 80 lb bags of concrete mix.
Concrete calculator
Volume is exact geometry. Weights and bag counts assume typical densities and bag yields — treat them as an estimate, not a quote.
How to use it
- Measure the length and width of the area in feet.
- Set the depth in inches.
- Pick the material, then read off the cubic yards (and bags or tons) you need.
The calculator multiplies area by depth for an exact volume, then converts to cubic yards and estimates weight or bag count from typical material figures.
How it's calculated
We multiply the area (length × width) by the depth to get the volume, then convert to cubic yards (27 cubic feet = 1 cubic yard). Where it helps we also estimate the weight from the material's typical density, or divide by the bag or pallet size — always rounding up so you don't come up short.
Frequently asked questions
- How many bags of concrete do I need?
- It depends on the volume. An 80 lb bag of concrete mix yields about 0.6 cubic feet and a 60 lb bag about 0.45 cubic feet. Enter your slab size above for the exact bag count.
- How much is a cubic yard of concrete?
- One cubic yard fills 27 cubic feet — for example a 9 ft × 9 ft slab at 4 inches thick. For large pours, ready-mix delivery is usually cheaper than bags.
- How thick should a concrete slab be?
- 4 inches is standard for patios and walkways; 5–6 inches for driveways or anything bearing vehicle weight.
Last updated June 2026.