How to work it out
π × (diameter ÷ 2)² × concrete depth × hole count × allowance factor ÷ bag yield- Diameter and depth must be in the same length unit.
- The calculator converts the cylindrical volume to cubic feet.
- It does not determine required hole geometry or whether concrete is appropriate.
Cylinder worksheet
| Input | Meaning | Do not substitute |
|---|---|---|
| Diameter | planned concrete cylinder width | radius |
| Depth | planned concrete fill depth | total excavation unless fully filled |
| Quantity | equal cylinders | mixed hole sizes |
| Yield | selected No. 1101 bag | another product’s label |
Plan the job
Confirm the installation detail
Use the fence, deck, mailbox, or equipment plan and local requirements to establish the actual fill geometry.
Measure groups separately
Put different diameters or depths in separate runs rather than averaging irregular holes.
Match the label
Select the exact 40, 60, or 80 pound No. 1101 bag in the calculator.
Before you start
- Locate utilities before digging and protect the excavation.
- Post and footing design must account for local soil, frost, wind, loads, drainage, and code.
Sources and notes
Source links reviewed July 16, 2026. A review date is not the document's publication date.
- 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.
- 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.