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Round Concrete Form Volume and Cost

Relate round form dimensions, concrete volume, supplied density, bag equivalents and material cost.

  • Formula & worked example
  • Private in your browser
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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

In initial displayed units, Volume 1, Quantity 2, Concrete density 2000, Bag size 25, Waste 10, Cost of each bag of pre-mix concrete 5 gives Weight 2000, Total volume 1.1, Bags needed 88, Total concrete cost 440, Cost per column 220.

Volume = π×diameter²×height×quantity/4; bag equivalents = volume×density×(1+waste)/bag mass.

Worked example

Enter these known values and leave the other values blank.

Volume
1 m³
Quantity
2 pieces
Concrete density
2000 kg/m³
Bag size
25 kg
Waste
10 %
Cost of each bag of pre-mix concrete
5 USD /bag
Height
6.85252 m
Weight
2000 kg
Equivalent concrete bags
88 bags
Cost of concrete per unit volume
440 USD / m³
Cost per column
220 USD /column
Equivalent bag material budget
440 USD

Assumptions and limitations

  • Form diameter presets use exact international inches. Density, bag mass and price are supplied product values. Bag equivalents are continuous; round up to whole bags when purchasing. Volumetric mix ratios are arithmetic planning recipes and do not predict strength, water demand or actual yield. The bag-based budget prorates the unrounded equivalent bag count; whole-bag purchase cost can be higher.
  • Use compatible measurement units. Clear an unknown before solving for it, and lock independent known values when comparing changes. Currency choices label amounts without exchange-rate conversion.

Common questions

Can I solve backward from the result?

Clear the unknown and enter independent known values. A rounded whole count cannot uniquely recover a continuous dimension; keep the original measured dimensions for procurement planning.

How many whole bags should I purchase?

Round the calculated mass-equivalent count upward to a whole bag and check the product yield. The mix-ratio options are volume arithmetic and do not certify concrete performance.

References

Enforce the stated physical geometry and whole-count domains. Bookify uses exact customary mass and volume definitions for density units, replacing rounded factors in the reference.

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