Concrete & foundations
Convert concrete volume into bags using mixed yield
Bag weight does not tell you how many litres of placed concrete it will produce.
Use the manufacturer's mixed yield for the exact concrete product. Bags of equal mass can have different yields, and a dry mass is not a finished volume. The order should remain traceable to the product label.
Work in litres or cubic metres consistently
An illustrative small pour needs 0.18 m³. That is 180 L. If the selected product's stated yield were 10 L per bag, the basic requirement would be 18 bags. With an illustrative 5% allowance it becomes 189 ÷ 10 = 18.9, rounded up to 19 bags. The 10 L rate is an example to replace with the actual product yield.
Count repeated shapes carefully
Six identical circular holes, each 0.3 m diameter and 0.6 m deep, have a gross volume of 6 × π × 0.15² × 0.6, approximately 0.2545 m³. This gross-hole figure has not deducted any embedded posts. Check whether your calculation includes displacement before interpreting it as a net fill quantity.
Decide whether the method is practical
Bag count is only part of the decision. Consider mixing capacity, placement time, water measurement, manual handling and access. A mathematical quantity does not establish a suitable concrete mix or a safe installation sequence.
Check the order basis
Record hole or slab dimensions, quantity, allowance, product yield and rounded bag count. The manufacturer's calculator or technical sheet is a useful independent check, but make sure it uses the same dimensions and allowance. Do not add extra water to obtain a larger yield.
Further reference
The worked numbers in this guide are illustrative unless a project record is identified.
Found a measurement or calculation issue? Send the example and your correction.