A 20 kg bag tells you its dry mass. To work out how many bags will fill a measured space, you need the volume of mixed concrete that the exact product produces. Then compare the rounded bag quantity with a ready-mix quote for the same planning volume and suitable product specification.
Hypothetical comparison: the 10 litre bag yield and all prices below are illustrative inputs, not current retail prices or supplier quotes. The separate Boral reference is sourced. Product suitability must be confirmed independently.
Find the mixed-concrete yield
Look for a yield in litres or cubic metres on the bag or the manufacturer's current product data sheet. Mixing-water quantity is not concrete yield. A bag of cement alone is not the same as a premixed concrete bag containing cement and aggregate.
For the specific Boral Concrete Mix reference used by our calculators, the product data sheet gives 108 × 20 kg bags per cubic metre. It is a reference for that product, not a universal rule. If your selected product instead states a yield of 10 litres per bag, use 10 litres for that calculation.
The same bag mass can give a different bag count
Start with the final planning quantity, not the geometric volume before its chosen allowance. One cubic metre is 1,000 litres, so 1.76 m³ = 1,760 litres. With the illustrative 10 litre yield, round up(1,760 ÷ 10) = 176 bags. With the Boral reference, round up(1.76 × 108) = 191 bags. Do not add another 10% merely because you have moved from the planner to a bag calculation.
Always round up to a whole bag at the end. For 1.765 m³ and a 10 litre yield, the unrounded requirement is 176.5 bags, so buy quantities would start at 177 bags before considering any supplier-specific pack arrangement. Keep full precision through the working rather than rounding every intermediate row.
Compare quoted material totals on the same basis
For an arithmetic exercise, suppose each 20 kg bag costs AUD $9.50 and a ready-mix quote is AUD $300 per cubic metre plus AUD $120 in quoted fees. These figures are deliberately labelled hypothetical; replace all of them with actual prices and compare quotes on a consistent tax basis.
| Option | Working | Material total |
|---|---|---|
| Illustrative 10 L yield | 176 bags × $9.50 | $1,672.00 |
| Boral 108 bags/m³ reference | 191 bags × $9.50 | $1,814.50 |
| Hypothetical ready-mix quote | 1.76 × $300 + $120 | $648.00 |
Try the hypothetical quote comparison
Clear the yield field in the calculator to compare the Boral reference. Entering a custom yield changes this comparison only; the single-pour calculators and project planner retain their stated Boral reference.
The lowest number in this table does not establish the best purchase. The example omits labour, equipment and any charges not entered. Product strengths, application limits, access and placement requirements may differ. A supplier minimum or a different quoted volume can also change what you actually pay.
Ask these questions before ordering
- Does the selected product meet the specification supplied for the job?
- Is the yield taken from the exact product's current label or data sheet?
- Does the supplier quote the same planning quantity, or apply a minimum load or ordering increment?
- Do both totals include the same tax treatment and all applicable delivery or other quoted fees?
- Are access, equipment and placement arrangements confirmed independently?
The arithmetic cannot decide concrete strength, post embedment, curing method, reinforcement or structural dimensions. Follow the selected manufacturer's instructions and the requirements supplied for your project.
Sources and checking
The comparison and illustrations are original hypothetical examples by ConcreteCalc. The 108-bag conversion is taken from Boral's Concrete Mix product data sheet, checked 31 October 2026. Refer to the manufacturer's product page and exact data sheet when using another product; we have not assigned the illustrative 10 litre yield to that product.
Our methodology documents the default assumptions. Report a calculation error with the page URL, inputs and result so we can reproduce it.