Concrete bag calculator
Calculate how many bags of pre-mix concrete (40lb, 60lb, or 80lb) you need for any slab, post hole or footing project.
Inputs
Results
80 lb bags
Enter your measurements to see the result
bags needed
60 lb bags
—
bags needed
40 lb bags
—
bags needed
Volume
—
cubic yards (yd³)
Buffer
10%
extra included
⚠ For large pours over 1 yd³, ready-mix concrete is more cost-effective than bags.
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Frequently asked questions
How many 80lb bags of concrete do I need?
One 80lb bag of concrete yields about 0.6 cubic feet (roughly 0.022 cubic yards). To find how many bags you need, multiply your total volume in cubic yards by 45.
How much volume does a 60lb bag of concrete make?
A 60lb bag of concrete yields approximately 0.45 cubic feet (about 0.017 cubic yards) of mixed concrete — multiply your volume in cubic yards by 60 to get the number of 60lb bags needed.
When should I use bags vs ready-mix concrete?
For pours under 1 cubic yard, pre-mix bags are usually more practical. For larger pours, ready-mix delivery is more cost-effective and saves significant labor.
How many 40lb bags of concrete do I need?
One 40lb bag of concrete yields about 0.3 cubic feet (roughly 0.011 cubic yards). You need approximately 90 bags per cubic yard of concrete.
How do I calculate concrete volume in cubic yards?
Multiply length × width × depth (all in feet), then divide by 27 to convert cubic feet to cubic yards.