🧱 Concrete Bag Calculator
Enter the concrete volume you need and a bag size to see how many bags of pre-mixed concrete to buy, including a 5% waste allowance and rounded up to whole bags.
🧱 Estimate Your Bag Count
What is a Concrete Bag Calculator?
A concrete bag calculator converts the volume of a pour into the number of pre-mixed bags to buy. Each bag size yields a fixed amount of mixed concrete, so the count is simply your volume divided by that yield, with a waste margin and rounding so you never come up short.
Enter the cubic feet you need — from a footing, a set of posts, or a small slab — choose a 40, 60, or 80 lb bag, and the tool returns the bags required. These are estimates for planning; verify with a structural engineer for load-bearing work.
❓ Frequently Asked Questions
How many bags of concrete do I need?
Divide the volume you need by the yield of one bag, then add a small waste margin and round up. An 80 lb bag yields about 0.60 cubic feet, a 60 lb bag about 0.45, and a 40 lb bag about 0.30. For 9 cubic feet with 80 lb bags, that is 9 ÷ 0.60 = 15, plus 5% waste rounds up to 16 bags.
Which bag size is most economical?
Larger 80 lb bags give the most yield per bag and usually the lowest cost per cubic foot, so they suit slabs and footings. Smaller 40 and 60 lb bags are easier to carry and handy for posts, small repairs, or jobs where you mix by hand a little at a time. The calculator lets you compare all three.
When should I order ready-mix instead of bags?
Bagged concrete is convenient up to roughly a cubic yard (about 45 to 90 bags depending on size); past that, mixing by hand becomes slow and inconsistent. For larger pours, a ready-mix truck delivered to the site is faster, more uniform, and usually cheaper per yard. Our concrete volume calculator helps you size that order.
Are these bag counts exact?
They are estimates for planning; verify with a structural engineer for load-bearing work. Actual yield varies a little with how stiff you mix the concrete and how much you spill, which is why a 5% waste allowance is built in and counts round up to whole bags.