Concrete Volume Calculator
Calculate the concrete required for a rectangular slab.
Slab Dimensions
Estimate only. Consider adding 5–10% for waste, spillage, and uneven subgrade.
Saved Entries
| Date | Dimensions | Volume | Bags (80 lb) | |
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Saved in this browser only — entries stay on this device unless you export them. Clearing browser data will erase this log.
How Concrete Volume Is Calculated
Concrete volume for a slab is simply length × width × thickness, converted into a single unit before multiplying. This calculator converts all three dimensions to meters internally, multiplies them to get cubic meters, then converts that figure into cubic feet and cubic yards — the units most US concrete suppliers quote by.
The bag estimate assumes a standard 80 lb bag yields about 0.6 cubic feet of mixed concrete, which is the manufacturer-stated figure for most pre-mixed bags sold at hardware and building supply stores. For anything beyond a small patch or footing, ready-mix delivery by the cubic yard is almost always more cost-effective than bagged concrete.