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MIKIPAL 09-26-2007 08:45 AM

how many 80 pound bags?
:) any help appreciated.have 10 --80 pound bags premix concrete.will it be enough for a 7 foot by 6 foot by 3.5 inches thick insulating hearth slab?thanx.

Les 09-26-2007 08:59 AM

Re: how many 80 pound bags?
You need around 14 cu ft of concrete. Most bags of concrete are 2/3 ft. Looks to me that you would need 21 bags.


asudavew 09-26-2007 09:38 AM

Re: how many 80 pound bags?
Yeah you need more.

I calculated 19 bags, but I would rather have a few too many, than a few too short.

Versachi 09-26-2007 03:09 PM

Re: how many 80 pound bags?
I used a couple of slab calculators which may help you out. The first one will give you the number of cubic yards needed (27 cubic feet in a cubic yard) and the second one allows you to enter the number of 80 pound bags you have and it will tell you how much concrete you will get. I threw in you numbers and asudavew's 19 bags seems like a good number!

Standard Pre-Mix Bag Concrete Quantity And Cost Calculator

Cheers, Versachi

Archena 09-26-2007 08:13 PM

Re: how many 80 pound bags?
Concrete Slab Calculator - The Concrete Network
Your link said 'page not found' but found the site. Sometimes they time out especially if you link to something already calculated. This one worked when I tested it.

christo 08-02-2009 12:56 PM

Re: how many 80 pound bags?
1 Attachment(s)
Here's the simple excel concrete calculator I made when I was pouring my benches and columns. Enter your dimensions in the yellow area.

It seems to work pretty well for 80 lb bags - I really haven't purchased 60lb bags - but it oughta work.

I used it so regularly during my construction phase I thought I'd send it along.


mfiore 08-02-2009 05:56 PM

Re: how many 80 pound bags?
Get a few extra. It's always easier to return a bag or two at your leisure later in the week than to race out like a madman in the middle of a pour.

christo 08-04-2009 03:40 PM

Re: how many 80 pound bags?
Been there done that for sure!

I always add an extra bag to the list. Maybe more if I over excavate or know I'll be pouring more soon.

I've had 3 bags sitting on top of a milk crate in the backyard covered by plastic for 6 months and they did not go hard on me. Keeping them dry and off the ground is key for storage.

When I was making my concrete cap stones, I was pretty happy with the accuracy of the calculations. Excavations are totally different.


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