Use this free concrete slab calculator to plan a home-improvement or DIY project from the measurements and product information you already have.
HomeCalc shows the formula behind the result and keeps product-dependent assumptions editable where possible, so the calculator can match the material, package or supplier you actually plan to use.
Enter slab dimensions and HomeCalc converts the volume to cubic yards, cubic feet and common bag counts.
FREE CONCRETE SLAB ESTIMATOR
Concrete Slab Calculator: Cubic Yards & Bags
Estimate concrete specifically for a rectangular slab from length, width and thickness.
Estimated result
Calculate a slab from footprint and thickness
For a rectangular slab, concrete volume is the footprint area multiplied by slab thickness. HomeCalc handles the inch-to-foot conversion for thickness and shows the result in units that are useful for ready-mix and bagged concrete planning.
length × width × thickness = slab volume
What to check before using the result
- Measure the inside dimensions of the forms where concrete will actually be placed.
- Check thickness across the whole excavation, especially after compacting the base.
- Thickened edges, beams and footings should be calculated separately when they are not uniform with the slab.
- Use an allowance when subgrade variation or placement conditions justify it.
Garage slabs, pads and structural slabs can include edge beams or localized thickening. Calculating those volumes separately and adding them to the uniform slab gives a more transparent estimate.