How It Works
Take the hassle out of math and simplify your concrete planning with our free concrete bag calculator.
With just a few easy steps, you can quickly determine the exact number of bags needed for your concrete project. Whether you plan on using 50, 60, 80 or even 90-pound bags, our app has you covered.
Let's start calculating!
Step-by-Step Tutorial
Calculating how many bags of concrete you need has never been easier. Follow these 3 simple steps to make the process seamless and efficient. Let's get started!
1. Choose Your Settings
Select your unit type, cost type (by bag or by the yard/meter), bag size, cost and desired waste amount. Your settings will be automatically saved for when you come back the next time.
2. Choose Your Shape(s)
We understand that many projects require multiple shapes or dimensions. Choose from a slab, footing, column, stairs, curb/gutter, circle/tube or any combination of them—it doesn't matter how many you have, we'll do the heavy lifting.
3. Add Your Dimensions
Once your shapes are added, input the dimensions that you've measured for each of them. After that, your results will be shown!
Pretty easy, isn't it?
Edit, Save and Repeat
Now you can easily measure all of your concrete projects. Bookmark this page and your calculations will be here when you return. When you're done, reset the calculator and start with a fresh one.
How Many Bags of Concrete Do I Need?
Here we breakdown some of the most common sizes of concrete slabs that are typically small enough to use bags.
Note: A good rule of thumb is that if the amount needed is over 1 yard, it'll be easier to have the concrete delivered by truck.
Determining the Number of Bags Needed
Planning a concrete project, whether it’s a small patio, a sidewalk, or a larger foundation, involves some important calculations to ensure you have enough materials on hand.
Here's how to determine how many bags of concrete you'll need for your project:
1. Measure the Area
Start by measuring the area where you will be pouring the concrete. You'll need to know the length, width, and depth (thickness) of the space. Use the following formulas based on your project type:
- Slab: Multiply length (L) by width (W) to get the area.
- Footing: Multiply the length (L) by the width (W) and then by the depth (D).
2. Calculate the Volume
Convert your measurements to feet (if they aren’t already) and use these formulas to calculate the volume:
- For rectangular projects: Volume = Length × Width × Depth
- For cylindrical projects: Volume = π × (Diameter / 2)2 × Depth
This will give you the volume in cubic feet. For most DIY concrete projects, depth is typically measured in inches, so be sure to convert inches to feet by dividing by 12.
3. Convert Volume to Bags of Concrete
Concrete bags are typically measured in cubic feet. A standard 80-pound bag of concrete mix yields about 0.6 cubic feet of concrete. To determine the number of bags you need, divide the total volume of concrete required by the yield per bag:
Number of Bags = Total Volume (cubic feet) / 0.6
For example, if your project requires 10 cubic feet of concrete:
Number of Bags = 10 / 0.6 ≈ 17 bags
4. Consider Waste and Variability
It's wise to buy extra bags to account for waste, spillage, and potential mistakes. A good rule of thumb is to add an extra 5-10% to your total number of bags. So, if you calculated that you need 17 bags, buying an extra bag or two would be prudent.
Extra Bags = 17 × 0.10 ≈ 2 bags
This brings the total to 19 bags.
5. Adjust for Different Bag Sizes
If you’re using bags of a different size (e.g., 60-pound or 40-pound bags), adjust the yield accordingly:
- 60-pound bag yields approximately 0.45 cubic feet.
- 40-pound bag yields approximately 0.3 cubic feet.
Recalculate the number of bags needed based on these yields:
Number of 60-pound Bags = Total Volume (cubic feet) / 0.45
Number of 40-pound Bags = Total Volume (cubic feet) / 0.3