Calculate how many bags of concrete (40, 60, or 80 lb) you need for your project based on slab dimensions.
Enter dimensions to calculate bags needed.
An 80 lb bag yields 0.6 cubic feet and costs less per cubic foot. A 60 lb bag yields 0.45 cubic feet and is easier to handle. A 40 lb bag yields 0.3 cubic feet.
Bagged concrete is practical for projects under 1 cubic yard. For larger projects, ready-mix concrete is cheaper and faster. Over 2 cubic yards, ready-mix is always recommended.
Mix one bag at a time in a wheelbarrow or mixer. Add water gradually — about 3 quarts per 80 lb bag. Over-watering weakens the final concrete.
About 45 bags of 80 lb concrete make one cubic yard (27 cu ft ÷ 0.6 cu ft per bag).
For projects under 1 cubic yard, bags work fine. Over 1 cubic yard, ready-mix is cheaper and faster.
Expertise covers cubic yard formulas, material planning, and ordering checks.