Concrete Calculator
Calculate the concrete volume and number of bags needed for a pour.
Result
Enter dimensions to calculate volume and bags needed.
Usage examples
Figuring out how many bags you need for a footing slab
Enter the slab's length, width, and depth to get the volume and the number of 40/60/80lb bags needed.
Estimating concrete for a round footing or post hole
For a cylindrical pour like a fence post or mailbox footing, just enter the diameter and depth.
Buying a safe margin of pre-mix bags
Add the suggested waste margin to the calculated bag count to avoid running short mid-pour.
Frequently asked questions
Where do the bag yield figures come from?
They're based on the standard published yields from widely-used US pre-mix brands like Quikrete and Sakrete (40lb≈0.3ft³, 60lb≈0.45ft³, 80lb≈0.6ft³). If your bag's packaging lists a more exact yield, switch to 'Custom' and enter it.
Why doesn't this automatically add a waste margin?
The right margin depends heavily on site conditions (subgrade flatness, formwork leaks, etc.), so we show the exact calculated volume and let you add the suggested 5-10% yourself based on your situation.
Does this calculate rebar or mix ratios too?
No. This tool only calculates concrete volume and bag count — it doesn't cover rebar layout or mix design.
Does switching between meters and feet lose my entered values?
No. Switching units automatically converts your entered dimensions, so you don't need to re-enter anything.