Concrete Volume Calculator
| Project | Dimensions | Volume (yd³) | 60 lb Bags | 80 lb Bags |
|---|---|---|---|---|
| Patio slab | 12 ft × 10 ft × 4 in | 1.63 | 88 | 65 |
| Porch footing | 40 ft × 1.5 ft × 1.5 ft | 3.33 | 180 | 137 |
| Round column | 1.5 ft Ø × 9 ft | 1.48 | 80 | 61 |
How the volume calculation works
Concrete is sold by the cubic yard, so the first step is converting the shape of your project into cubic feet and then dividing by 27. For a rectangular slab the formula is , where length, width, and thickness are measured in feet. Cylindrical columns use the expression . After the base volume is computed, the calculator applies your waste percentage so you can cover over-excavation, spillage, or uneven forms.
Because many small projects rely on bagged concrete, the tool also estimates how many 60 and 80 pound bags match the yardage. Multiplying the yardage by 54 or 41 converts cubic yards to bag counts, reflecting the typical yield per bag once mixed. If you enter a ready-mix price, the result highlights a materials budget so you can compare bulk delivery against purchasing bags locally.
Planning a successful pour
Measure inside the forms at multiple points to capture the smallest length, width, and thickness—irregular trenches can create large swings in required volume. Always round up once you apply waste; running short mid-pour is more costly than disposing of a small surplus. For hand-mixed bags, stage materials close to the project and pre-fill buckets with water so you can maintain a consistent mix. Ready-mix deliveries need unobstructed access for trucks or a pump if the forms sit far from the street.
What to do after calculating volume
Knowing the volume lets you schedule reinforcement, finishing tools, and curing supplies. Pair this calculator with the Concrete Mix Design Calculator, Concrete Formwork Pressure Calculator, and Deck Footing Concrete Volume Calculator to finalize mix proportions, confirm form strength, and double-check supporting footings. Keeping these estimates together helps you communicate confidently with suppliers and crew members.