Pro Tip
Estimating Bagged Concrete Jobs
Working with concrete can create a bit of anxiety, no matter how big or small the job—whether you’re placing a slab, leveling out a space for a patio or setting posts.
The first and most important step for any concrete project is to work out the volume of concrete needed – which isn’t always easy, even for pros who are used to working in cubic yards.
“A quick rule of thumb: one pallet of bags is about a cubic yard of concrete.
Though it actually takes 45 bags of 80-pound mix to hit a cubic yard dead on, this is a great method to get a good initial estimate.
Visualizing how far a cubic yard isn’t always intuitive, but there’s an easy reference point: 9’ x 9’ slab at 4” deep, or about five sidewalk squares.
In other words, 1 cubic yard of concrete placed at 4-inches deep will cover 81 square feet.
ESTIMATING THE OLD-FASHIONED WAY
The formula for estimating the volume of concrete in cubic yards needed on a project is straight forward, though it will definitely require a calculator.
Simply multiply the length by the width by the depth of the desired slab in inches, then divide by 1728. The result is the total cubic feet of the slab.
To get to cubic yards, divide that number by 27.
“It’s always a good idea to add 10% to every estimate.
ESTIMATING SHORTCUTS
Another shortcut method requires knowing a little bit about how far a single bag of concrete will go.
“The trick: one square foot of concrete equals:
1x 50# bag
0.8x 60# bags or
0.6x 80# bags
Though this method only works with a 4” slab, it’s a single calculation that also automatically works in the 10% waste factor, making it a great standby.
For example, if you have a 9’ x 9’ slab at 4” deep, you have a total of 81 square feet. If you’re using 80# bags, you multiply the total square footage (81) by 0.6 to get 48.6 bags – a bit on the high side, but in concrete it’s always better to be safe than sorry.
SKIP THE MATH
Sakrete has concrete calculators for every type of project to make estimating even easier. From new pours to repairs, resurfacing, masonry work and more, there’s a calculator for your job.
“There’s a concrete calculator for your job.
Just punch in the dimensions of your job, and the calculators will provide the exact number of bags, recommended products, and provide Project Pro Tips guides to help you get the job done right.
ESTIMATING IRREGULAR POURS
Not all jobs are easy rectangles. Adding concrete footings to posts or laying an irregularly shaped or curved slab can require meticulous measuring, or make you dust off your old geometry book, which will inevitably slow you down.
“Solution? The Sakrete App.
The App uses AR spatial technology to measure and scan project sites to quickly calculate the number of concrete bags needed for slab, post, or repair projects – as well as recommending the right product for the job, and connecting you to your local dealer. Nothing easier than that!
GET THE JOB DONE RIGHT
Spot-on estimates are just the first step in tackling your next project. For everything else, make sure to check out our Project Pro Tips Guides for step-by-step guidance on the most common jobs, and remember to give us a call at 866-SAKRETE with any questions!
Comments (18)
Now that was great now I can pour my own driveway
Nice
I’m interested in this calculator
Seems really good how do I apply for it
Thanks
How many bags do we need to pour a 10×12 two inch slab?
That’d be about 45 bags…but add 10% to be safe and round up to 50!
Good job
Amount of cement to do 10 foot by 1 foot by 1.5 inches
That’d be 4 bags…but add 1 more for safety!
How many bags of concrete for a 4 foot by 6 foot by 3 inch slab
Sandy, that’s about 14 60# bags…but add 10% and round up to 16 to be safe!
Just wondering how many bags of concrete would I need to fill the insides of 240 8”x8”x16” Blocks?
Roughly 96. Our sister brand, Amerimix, has a great grout calculator for future reference!
How long will an open bag of Sakrete be used?
It’s going to depend on where it was stored and how much moisture is in the air. Most important note: if it’s hardened, it’s no good.
How many 80lb bags for 14×4 @ 3” Deep?
And, do you need to add sand or lime for a driveway pour?
That’d be 24 bags…but always a good idea to add 10% for variance, so round up to 27 bags!
No need to add anything to bagged mixes for ANY application – everything you need to reach stated performance is right in the bag!
Final point…if this 14×4 slab is for a driveway, definitely need to go deeper than 3″. A minimum of 4″, but 5 – 6″ on a driveway is even better!