How many bags of cement do I need to make 1 cubic metre of concrete?

Written by James McDonald


December 30, 2011

Currently (Dec 2011) doing fence posts and some small concrete pads around the house so I need to self mix the concrete

Here is a good example of what is required from the “General Purpose Cement Product Data Sheet” on Boral’s Site

General Purpose Cement Product Data Sheet

From my learnings if you mix in the following shovel fulls of Cement/Sand/Aggregate you will use approximately the following bags of cement per m3 of concrete

CementSandAggregate (gravel)Bags of 20kg General Purpose Cement per Cubic MetreComment
12316Strong but costly
12.5413Good for fence posts

The more cement the more costly of course so don’t over do it.


  1. Jonathan

    Can you assist by confirming how many 40kg bags of cement do I need per cubic metre volume?


    • James

      If it’s 13 bags of cement for 20kg bags it will be 6.5 bags of cement for 40kg bags.

      • Phillip

        Are you sure that’s 20 kg of cement per bag james?

        • James McDonald

          I’m not sure if I understand exactly what you mean, but in Australia the standard weigh for a bag of cement is 20kg.

    • Bob

      How many 20kg general purpose ready mixed concrete bags do i need for .56 cubic metres

  2. James

    If it’s 13 bags of cement for 20kg bags it will be 7.5 bags of cement for 40kg bags.

  3. Jarod

    I found from Boral 1m3 of cement you need 108 20kg bags (54-40kg) premix bags or For a one 20 kg bag equals 0.01m3.

    This should be easier to understand.

    • Damien

      Great thanks Jarod

  4. Allan O'Rourke

    How many bags of concrete do I need for a 3.1m x 3.1m x 110mm slab?

    • Drew

      C’mon Allan – thats just lazy ?
      3.1 x 3.1 = 9.61m2 x 0.11 = 1.05m3

      James’ estimates for 1cubic meter will be close enough for your slab.


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