how much area does an 80lb bag of concrete cover?
 

I'm building a new shed, I'm going to buy the 80 lb bags from Home Depot. The depth will be about 4" (using a 2x4). How much coverage will each bag give me?

Thanks, KarlJay.

Here's a calculator
 

The calculator at this site, Concrete Volume Calculator , will take your measurements and tell you how many bags (various sizes), cu ft or cu yards the job will require.
I ran a calc to find that 1 cu ft requires 1.7 80'lb bags....so one bag is about .6 cu ft.

more than you think it will, there is a chart on the side of the bag that will help you figure how many bags

Lay the bag down on the ground. That is about how much it will cover.

Using a 10x12 shed as a starting point, it will take you 67 bags. Also, if you simply lay 2x4s on the ground the concrete will just lift them up and flow under them, or bow/push them out of the way.

QUIKRETE® - Cement and Concrete Products has a materials calculator right on their website.

Steve

For the amount I wouldnt know so im assuming Ford_6 is correct for laying the slab. When buying 2x4s get the straightest ones possible. To prevent bowing of the boards (which berely ever happens on this small of a slab) put a stake every 2 feet or so on each board. Then get a draw string to go across the forms to put a stake or two in the central area of the slab for "grade stakes" so when you pour the concrete in the middle.

When you have reached the middle you will know what height (same height as 2x4s) to screet the mud to for being flat from those grade stakes. Screeting can be done with a NON bowed or warped board so you don't have dips in the concrete. If you already knew this I guess I just remided you of it but good luck.

lots of bags
 

67 Bags? thats a lot of 80 lb bags to lug home from Home Depot. Check in theYellow Pages for concrete companies that will mix and deliver short loads on site.

how much coverage per bag?
 

An 80lb bag yields 2/3 of a cubic ft per bag.
You will get 2 sq ft of coverage @ 4" thickness. Dont run out of bags in the middle of a pour!

concrete
 

If he goes to a ready-mix company it might be more expensive since there is a delivery fee most likely & the price of mud has gone up also. I think from what I remember on our last job, the company we used it was 300 bucks for 2 - 1/2 yards of mud. So if he has a big bin and two guys mixing with shovels I am sure it will go fine.

Like mitchntx said, the coverage is the same as the bag laid on the ground, you add water to it but it does not swell up, Naturally you can use the concrete calculator for large jobs, but I (at Lowe's) always tell folks it they are pouring a sidewalk or stepping stones the bag size is what it will be once mixed.
later, Mike

Also take a look in the phone book to see if there's a U-Cart company -- they have a small cart that carrys about 1 - 2 yards of concrete they've mixed, all you do is haul it to your house and dump it into your forms. The problem with mixing that much bag concrete is that the first bags you mix are drying by the time you're mixing the last bag unless you're fast.