How do I calculate bags of concrete?

Short answer

Calculate cubic volume, divide by the exact selected bag’s stated approximate yield, and round the final quotient up to a whole bag.

Current QUIKRETE No. 1101 documentation lists about 0.30 ft³ for 40 lb, 0.45 ft³ for 60 lb, and 0.60 ft³ for 80 lb. The product is for placements at least 2 inches (50 mm) thick.

  • Do not mix yields from different bag sizes or products.
  • Use finished concrete dimensions.
  • Design, reinforcement, base, joints, and curing remain separate decisions.

Formula or decision boundary

adjusted cubic feet ÷ selected bag cubic-foot yield; round up

Current No. 1101 yield rows

Current No. 1101 yield rows
BagStated approximate yieldPurchase rule
40 lb0.30 ft³ / 8.5 Lround up
60 lb0.45 ft³ / 12.7 Lround up
80 lb0.60 ft³ / 17 Lround up

Use the answer

  1. Calculate geometry

    Use a rectangular or cylindrical formula that matches the actual placement.

  2. Select the bag

    Match the exact No. 1101 size stocked for the project.

  3. Round the quotient

    Keep full precision until after dividing adjusted volume by yield.

Safety and scope

  • Wet cement can cause serious burns; follow product safety instructions.
  • Verify excavation, structural, frost, utility, and code requirements locally.

Sources and scope

Source links reviewed July 16, 2026. A review date is not the document's publication date.

  1. QUIKRETE: Concrete Mix No. 1101 Technical Data SheetNorth America · manufacturer data sheet

    Bag counts are based on stated approximate yield and must be rounded up to whole bags.

  2. National Institute of Standards and Technology: NIST Guide to the SI, Appendix B — Conversion FactorsUnited States · government standard

    Code retains exact defining constants where NIST identifies an exact relationship.