I would like to make a small concrete slab of the following dimensions.

Length: 1.2m
Width: 0.86m
Depth: 0.09m

The cubic volume as i understand it is all those numbers multiplied.
result: 0.0929m2

If a bag of pre-mix concrete says
0.2m2 x 50mm

How many bags would I need?

Update: Brick BBQ construction. I am doing this for "homework" :) enter image description here

  • 1
    Your volume should be in cubic meters. Trivial, but true.
    – Tim Quinn
    Nov 30, 2012 at 0:03

1 Answer 1


I would say 10 or 11 bags (depending on how sloppy you are).

0.2 * .05 = .01

.0929 / .01 = 9.29 bags

Since you never get perfect yield from a bag, I would personally go with 11 bags.

  • It might be that it actually says a square .2 meters on a side. This seems a more likely way of specifying the useful volume of the bag. Just in case that makes your numbers off by 1/2. The number in that case would be 19 or 20 bags.
    – Tim Quinn
    Nov 30, 2012 at 0:12
  • Looking again, this looks like a homework problem, so it doesn't have to reflect common sense at all.
    – Tim Quinn
    Nov 30, 2012 at 0:18
  • 2
    "Homework"? I guess it is. See my in progress home work LOL. Have updated my post. The calculation was quite accurate. After resizing the slab, we calculated 12 bags. I bought 14 and returned 1 back to the shop.
    – Valamas
    Nov 30, 2012 at 2:03
  • Nice work, Valamas.
    – Tim Quinn
    Nov 30, 2012 at 8:52
  • Glad it worked out for you! Very nice fire place too!
    – Dave Nay
    Nov 30, 2012 at 13:36

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.