CONCRETE PLANNING
How many bags of concrete do I need?
Concrete bag count depends on the volume of your pour and the yield of the specific bag you plan to buy. Measure the project first, then convert the required volume into bags.
The basic calculation
Multiply length × width × thickness to find volume. When length and width are in feet, convert thickness from inches to feet by dividing it by 12. That gives cubic feet. Divide by 27 if you also want cubic yards.
To estimate bags, divide the required cubic feet by the yield per bag printed on the concrete product. Always round the bag count up because partial bags do not cover a shortfall.
Example: 4 ft × 4 ft × 4 in pad
A 4-by-4-foot pad that is 4 inches thick requires about 5.33 cubic feet of concrete. If the bag you choose yields 0.60 cubic feet, 5.33 ÷ 0.60 = 8.89, so the planning estimate is 9 bags.
Before buying
- Use the yield printed on the exact bag size and mix you are purchasing.
- Recheck slab thickness because even a small thickness change can materially change volume.
- Irregular excavations can require more material than neat rectangular dimensions suggest.
- Large pours may be more practical with ready-mix concrete than individual bags.