Material calculator
Concrete Bag Calculator
Use your chosen product’s mixed yield to work out how many bags to buy.
Your measurements
Changing units changes the display, not the stored measurement.
Results
Example inputs
Your result will appear here
Enter the measurements and product details, then calculate.
These tools estimate material quantities from dimensions you choose. They do not specify structural depth or load capacity.
Copy the mixed yield from the product information
Enter the volume of mixed concrete produced by one bag. This is a volume, such as cubic metres or cubic feet, not the dry weight printed most prominently on many bags. Products and package sizes can have different yields; PackLedge does not assume that every bag with the same mass produces the same volume.
Keep the source unit where possible. If a label gives two rounded equivalent yields, choose one source value and unit rather than treating both as exact measurements. The estimate is only as applicable as the yield you supply.
Choose the volume basis
Start from the net measured volume and apply your chosen allowance once. If you already have a required volume that includes an allowance, do not add it again. The bag result is the smallest whole number of bags whose entered yield covers that required volume.
Example: exactly on a bag boundary
A net slab volume of 0.6 m³ with a chosen 10% allowance requires 0.66 m³. With an illustrative user-entered yield of 0.012 m³ per bag, 0.66 ÷ 0.012 is exactly 55. The order is 55 bags, supplying 0.66 m³. An internal rounding error should not turn this into 56 bags.
If the real required amount is slightly greater than that boundary, an additional bag may be necessary. A display rounded to two decimal places must not conceal the extra requirement.
Combine compatible volumes before rounding
Two areas using exactly the same product and bag yield can share a purchase group. Add their unrounded requirements, then round to whole bags. Adding separately rounded bag counts can produce a larger purchase, which may be appropriate for separate orders but is a different choice.
Confirm the product and the pour
This tool does not choose a mix, bag size or allowance and does not assess construction suitability. Keep the product description and yield with the result so the shopping list remains meaningful.
Frequently asked questions
Can I enter bag weight instead of yield?
No. Weight alone does not establish the volume of mixed concrete. Find the mixed yield for your selected product and package.
Are extra whole bags the same as my allowance?
No. The allowance is a percentage you choose before purchasing. Whole-bag rounding can add further volume, which is shown as purchase surplus.
Sources and method
- PackLedge quantity methods
Original derivations using geometry, ratios, sums and whole-package rounding. Each calculator explains its assumptions and worked examples.
- Your selected product label or technical sheet
The source for the coverage, mixed yield, density, package capacity, sheet dimensions or wallpaper repeat that you enter.