Calculator 01 / Concrete
Concrete Calculator
Figure cubic yards and bag count for slabs, footings, round columns, and stairs. Enter your measurements, pick a shape, and add a waste buffer before you order.
How this calculator works
Concrete volume is length × width × thickness, converted to cubic feet and then to cubic yards (concrete is sold by the cubic yard for ready-mix, or by the bag for small pours). This tool applies the same formulas ready-mix suppliers and bagged-mix manufacturers use:
The stairs formula treats each step as a stacked rectangular block, which is the standard approximation used for a solid stair pour (no separate stringer or void beneath).
How much waste factor should I add?
5–10% covers most slab pours. Add more (10–15%) for uneven or unexcavated subgrade, hand-dug footings, or irregular forms where over-digging is likely.
When should I order ready-mix instead of bags?
As a rule of thumb, pours over roughly 1 cubic yard (about 60–70 bags of 60 lb mix) are usually cheaper and faster with a ready-mix delivery than hand-mixing bags.
Does this account for rebar or wire mesh volume?
No — reinforcement takes up a negligible fraction of pour volume and is not subtracted. This calculator estimates gross concrete volume only.
Estimates only. Confirm final quantities with your ready-mix supplier or bagged-mix manufacturer, and always order slightly more than the calculated minimum.